# \#assertion-failed **URL:** https://forums.unrealengine.com/tag/assertion-failed/3974.md [Latest](https://forums.unrealengine.com/latest.md) · [Categories](https://forums.unrealengine.com/categories.md) · [Tags](https://forums.unrealengine.com/tags.md) --- ## [Unreal Engine 5.6.1 Continues to crash when running a MQTT connection.](https://forums.unrealengine.com/t/unreal-engine-5-6-1-continues-to-crash-when-running-a-mqtt-connection/2720619)
**Author:** [@AddisonCtrlDevs](https://forums.unrealengine.com/u/AddisonCtrlDevs)\ **Replies:** 1\ **Last updated:** [October 29, 2026, 6:29pm UTC](https://forums.unrealengine.com/t/unreal-engine-5-6-1-continues-to-crash-when-running-a-mqtt-connection/2720619 "2026-10-29T18:29:45Z")
Good Morning All! (Quick preface, I am running this project on 5.6.1 and am attempting to use the built in experimental MQTT plugin) I am still trying to learn and experiment with MQTT implementation within UE5 bluepri… --- ## [Crash : Assertion failed: FVector::Distance(Initializer.ViewRotationMatrix.GetScaleVector(), FVector::OneVector) \< (1.e-4f)](https://forums.unrealengine.com/t/crash-assertion-failed-fvector-distance-initializer-viewrotationmatrix-getscalevector-fvector-onevector-1-e-4f/477932)
**Author:** [@Aherys](https://forums.unrealengine.com/u/Aherys)\ **Replies:** 12\ **Last updated:** [June 7, 2026, 9:02pm UTC](https://forums.unrealengine.com/t/crash-assertion-failed-fvector-distance-initializer-viewrotationmatrix-getscalevector-fvector-onevector-1-e-4f/477932 "2026-06-07T21:02:57Z")
Way to reproduce : Happening when in editor we navigate with the camera in editor + right mouse bouton (very often, and very fast if we do a “long use” of camera navigation). Engine suddently crash with this assert. En… --- ## [Assertion Failed](https://forums.unrealengine.com/t/assertion-failed/2688627)
**Author:** [@rECOMBINAToR](https://forums.unrealengine.com/u/rECOMBINAToR)\ **Replies:** 2\ **Last updated:** [December 31, 2025, 12:06pm UTC](https://forums.unrealengine.com/t/assertion-failed/2688627 "2025-12-31T12:06:37Z")
Hi Guys, I got this error continuously, ‘kinda’ randomly: \[2025.12.30-19.09.36:566\]\[162\]LogWindows: Error: appError called: Assertion failed: SyncPosition.NextMarkerName != NAME\_None \[File:D:\\build++UE5\\Sync\\Engine\\Sou… --- ## [UE4.26 Niagara Assertion Failed Crash Randomly](https://forums.unrealengine.com/t/ue4-26-niagara-assertion-failed-crash-randomly/485988)
**Author:** [@ycz](https://forums.unrealengine.com/u/ycz)\ **Replies:** 18\ **Last updated:** [October 7, 2025, 2:01pm UTC](https://forums.unrealengine.com/t/ue4-26-niagara-assertion-failed-crash-randomly/485988 "2025-10-07T14:01:25Z")
I created a Infinite life particle(with no update modules,just some random particle) and placed it under a static mesh like No physic enable,just static,all default setting,random crash when PIE like: Assertion… --- ## [Assertion failed: bUncompressMemorySucceeded](https://forums.unrealengine.com/t/assertion-failed-buncompressmemorysucceeded/468914)
**Author:** [@sayooj\_js](https://forums.unrealengine.com/u/sayooj_js)\ **Replies:** 8\ **Last updated:** [February 22, 2025, 2:04am UTC](https://forums.unrealengine.com/t/assertion-failed-buncompressmemorysucceeded/468914 "2025-02-22T02:04:40Z")
Assertion failed: bUncompressMemorySucceeded \[File:D:/Build/++UE4/Sync/Engine/Source/Runtime/Core/Private/Serialization/Archive.cpp\] \[Line: 683\] Failed to uncompress data in C:/Users/SAYOOJ/Documents/Unreal Projects/Juno… --- ## [UE 5.3 -- Assertion failed: Index == TypeIndex](https://forums.unrealengine.com/t/ue-5-3-assertion-failed-index-typeindex/1294524)
**Author:** [@FireFist\_38](https://forums.unrealengine.com/u/FireFist_38)\ **Replies:** 33\ **Last updated:** [February 4, 2025, 3:32pm UTC](https://forums.unrealengine.com/t/ue-5-3-assertion-failed-index-typeindex/1294524 "2025-02-04T15:32:29Z")
I was working on a project all night (UE 5.3) with no issues, and after closing it and trying to get back on the next day, the project crashes immediately on startup. The most recent things I was doing within the projec… --- ## [Game crash with launch on mobile](https://forums.unrealengine.com/t/game-crash-with-launch-on-mobile/324853)
**Author:** [@skeleton60](https://forums.unrealengine.com/u/skeleton60)\ **Replies:** 2\ **Last updated:** [January 19, 2016, 6:59pm UTC](https://forums.unrealengine.com/t/game-crash-with-launch-on-mobile/324853 "2016-01-19T18:59:08Z")
When i try to launch my mobile game on my nexus 5, game crash, any map crash on launch any idea? :o Here is log from LogCat 07-11 14:26:06.669: D/UE4(25802): In the JNI\_OnLoad function 07-11 14:26:06.669: D/UE4(25802)… --- ## [Getting strange error on dedicated server (Assertion failed: NetGUID.IsDynamic())](https://forums.unrealengine.com/t/getting-strange-error-on-dedicated-server-assertion-failed-netguid-isdynamic/1181564)
**Author:** [@ackyshacky](https://forums.unrealengine.com/u/ackyshacky)\ **Replies:** 11\ **Last updated:** [December 20, 2024, 9:45am UTC](https://forums.unrealengine.com/t/getting-strange-error-on-dedicated-server-assertion-failed-netguid-isdynamic/1181564 "2024-12-20T09:45:39Z")
Hello everyone, I have a multiplayer shooter game (UE 5.0.3) running on a dedicated server. As the client, when I do a line trace from the gun to a specific blueprint (called BP\_StreetLight), the engine crashed with the… --- ## [\[SOLVED\] Assertion failed: Mesh && Mesh-\>GetRenderData()](https://forums.unrealengine.com/t/solved-assertion-failed-mesh-mesh-getrenderdata/1269505)
**Author:** [@FiendCorp](https://forums.unrealengine.com/u/FiendCorp)\ **Replies:** 5\ **Last updated:** [October 30, 2024, 8:58pm UTC](https://forums.unrealengine.com/t/solved-assertion-failed-mesh-mesh-getrenderdata/1269505 "2024-10-30T20:58:37Z")
Hello, Before I upgraded my project to UE5 from UE4.27, I was able to package without issue. Now i am getting: “PackagingResults: Error: appError called: Assertion failed: Mesh && Mesh-\>GetRenderData() \[File:D:\\build++U… --- ## [Lightmass static lightning timed-out, asserts mismatch in task counting](https://forums.unrealengine.com/t/lightmass-static-lightning-timed-out-asserts-mismatch-in-task-counting/457350)
**Author:** [@anonymous\_user\_6f3f79f9](https://forums.unrealengine.com/u/anonymous_user_6f3f79f9)\ **Replies:** 5\ **Last updated:** [October 2, 2024, 6:28am UTC](https://forums.unrealengine.com/t/lightmass-static-lightning-timed-out-asserts-mismatch-in-task-counting/457350 "2024-10-02T06:28:13Z")
I’m building lightning in UE 4.23.0 on Ubuntu 16.04 and, following the logs, when static lightning needs to be built it gets timed out. Later, in the logs, an error LogInit: Error: Timed out waiting for the recipient (Ti… --- ## [Assertion failed: UploadBufferSize \>= UploadBytes crash](https://forums.unrealengine.com/t/assertion-failed-uploadbuffersize-uploadbytes-crash/1911765)
**Author:** [@j-jan](https://forums.unrealengine.com/u/j-jan)\ **Replies:** 0\ **Last updated:** [June 21, 2024, 5:01pm UTC](https://forums.unrealengine.com/t/assertion-failed-uploadbuffersize-uploadbytes-crash/1911765 "2024-06-21T17:01:08Z")
Assertion failed: UploadBufferSize \>= UploadBytes UnrealEditor\_Engine UnrealEditor\_Engine UnrealEditor\_Renderer UnrealEditor\_Renderer UnrealEditor\_Renderer UnrealEditor\_Renderer UnrealEditor\_Renderer UnrealEditor\_Core U… --- ## [CumulativeLODSizes Assertion Failed error in packaged build](https://forums.unrealengine.com/t/cumulativelodsizes-assertion-failed-error-in-packaged-build/1852613)
**Author:** [@nikbot2](https://forums.unrealengine.com/u/nikbot2)\ **Replies:** 0\ **Last updated:** [May 12, 2024, 2:56pm UTC](https://forums.unrealengine.com/t/cumulativelodsizes-assertion-failed-error-in-packaged-build/1852613 "2024-05-12T14:56:52Z")
(Sorry if this is an duplicate question or I used wrong topic for this) I tried doing a test package of a project I was working on, using Unreal Engine 4.27.2, and it plays fine in editor using standalone game mode, and… --- ## [Vulkan RHI causing regular engine crash. Assertion failed error.](https://forums.unrealengine.com/t/vulkan-rhi-causing-regular-engine-crash-assertion-failed-error/479354)
**Author:** [@Noxxie](https://forums.unrealengine.com/u/Noxxie)\ **Replies:** 7\ **Last updated:** [April 4, 2024, 9:47pm UTC](https://forums.unrealengine.com/t/vulkan-rhi-causing-regular-engine-crash-assertion-failed-error/479354 "2024-04-04T21:47:25Z")
Hey guys, So I’m working with Vulkan in a Source build of Unreal, and I get a reoccuring crash with the same error whenever I’m doing pretty much anything with a very high poly (~3 Milllion Triangles) static mesh, the c… --- ## [Engine crashs randomly with Assertion failed.. when just closing any Blueprint](https://forums.unrealengine.com/t/engine-crashs-randomly-with-assertion-failed-when-just-closing-any-blueprint/1761176)
**Author:** [@BDC\_Patrick](https://forums.unrealengine.com/u/BDC_Patrick)\ **Replies:** 1\ **Last updated:** [March 22, 2024, 2:52pm UTC](https://forums.unrealengine.com/t/engine-crashs-randomly-with-assertion-failed-when-just-closing-any-blueprint/1761176 "2024-03-22T14:52:27Z")
Since 5.3 I got the Problem, that the whole Editor crashes fatally with this Error: LoginId:5e2c7109436d056ad49530a6393c8e42 EpicAccountId:5d02987cf41f4199a7111db08716aee2 Assertion failed: IsValid() \[File:D:\\build\\++U… --- ## [Assertion failed: Actor-\>Brush-\>RootOutside](https://forums.unrealengine.com/t/assertion-failed-actor-brush-rootoutside/483545)
**Author:** [@kokostas2001](https://forums.unrealengine.com/u/kokostas2001)\ **Replies:** 2\ **Last updated:** [February 23, 2024, 4:42pm UTC](https://forums.unrealengine.com/t/assertion-failed-actor-brush-rootoutside/483545 "2024-02-23T16:42:37Z")
hello i have a big map and when i try to build either lighting either geometry unreal crash and i cant even build the lighting for the project Assertion failed: Actor-\>Brush-\>RootOutside \[File:D:/Build/++UE4/Sync/Engine… --- ## [Un5 is crashing on start a project.](https://forums.unrealengine.com/t/un5-is-crashing-on-start-a-project/1696860)
**Author:** [@DeanFromTokyo](https://forums.unrealengine.com/u/DeanFromTokyo)\ **Replies:** 1\ **Last updated:** [February 18, 2024, 10:59am UTC](https://forums.unrealengine.com/t/un5-is-crashing-on-start-a-project/1696860 "2024-02-18T10:59:09Z")
Hey y’all, My project keep crashing on start. What I did was I clicked to package the project. Then, I tried to open the console log. UN crashed that time. Since then I cant open the project. Error log shows this: Scr… --- ## [Assertion failed: RecursionNotAllowed.Increment() == 1](https://forums.unrealengine.com/t/assertion-failed-recursionnotallowed-increment-1/399244)
**Author:** [@LazerTale](https://forums.unrealengine.com/u/LazerTale)\ **Replies:** 35\ **Last updated:** [September 7, 2023, 1:09pm UTC](https://forums.unrealengine.com/t/assertion-failed-recursionnotallowed-increment-1/399244 "2023-09-07T13:09:15Z")
Hey AvikB- Thank you for submitting a bug report. I have reproduced this issue and logged a report for it here Unreal Engine Issues and Bug Tracker (UE-46610) . You can track the report’s status as the issue is reviewed… --- ## [Assertion Failed Crash: SerializeNum](https://forums.unrealengine.com/t/assertion-failed-crash-serializenum/491332)
**Author:** [@AdamBaker2](https://forums.unrealengine.com/u/AdamBaker2)\ **Replies:** 2\ **Last updated:** [July 27, 2023, 2:01pm UTC](https://forums.unrealengine.com/t/assertion-failed-crash-serializenum/491332 "2023-07-27T14:01:09Z")
LoginId:a1a5dc4a4132c9d353db9293971927e1 EpicAccountId:44a4344e3fca4f9b9eb555014970156b Assertion failed: SerializeNum \>= 0 \[File:D:\\Build++UE4\\Sync\\Engine\\Source\\Runtime\\Core\\Public\\Containers/Array.h\] \[Line: 1152\] U… --- ## [Lightmass crashed: Assertion failed and more](https://forums.unrealengine.com/t/lightmass-crashed-assertion-failed-and-more/414662)
**Author:** [@MinhMX](https://forums.unrealengine.com/u/MinhMX)\ **Replies:** 22\ **Last updated:** [May 19, 2023, 5:14pm UTC](https://forums.unrealengine.com/t/lightmass-crashed-assertion-failed-and-more/414662 "2023-05-19T17:14:00Z")
Hi guys, I got a problem. When I clicked Build, after a short time, the Message Log appeared with the error: Lightmass crashed: Assertion failed … and so many things below. Please see the image below. So hope you guy… --- ## [Feature Request: Specify Problem Variable/Array In "Assertion Failed: Index \> ArrayNum" Error](https://forums.unrealengine.com/t/feature-request-specify-problem-variable-array-in-assertion-failed-index-arraynum-error/773733)
**Author:** [@king-worm](https://forums.unrealengine.com/u/king-worm)\ **Replies:** 0\ **Last updated:** [February 18, 2023, 10:34pm UTC](https://forums.unrealengine.com/t/feature-request-specify-problem-variable-array-in-assertion-failed-index-arraynum-error/773733 "2023-02-18T22:34:56Z")
So I’ve seen this error come up a lot online and am currently dealing with this myself in my own project. While I am aware of what causes the issue (trying to get an index outside of the array’s bounds), without proper k… --- ## [UE5.1 Editor crash on Lightmass build: Assertion failed in NaniteMaterials.h](https://forums.unrealengine.com/t/ue5-1-editor-crash-on-lightmass-build-assertion-failed-in-nanitematerials-h/747045)
**Author:** [@OneNot](https://forums.unrealengine.com/u/OneNot)\ **Replies:** 0\ **Last updated:** [January 11, 2023, 1:37pm UTC](https://forums.unrealengine.com/t/ue5-1-editor-crash-on-lightmass-build-assertion-failed-in-nanitematerials-h/747045 "2023-01-11T13:37:32Z")
Hi, Working on a UE5.1 project in a large scene with tons of geometry brought in via Datasmith and converted to Nanite. Decided to try out Lightmass, but building lights crashes the engine without fail pretty much insta… --- ## [Assertion Failed: AsyncLoading.cpp, Line 3710](https://forums.unrealengine.com/t/assertion-failed-asyncloading-cpp-line-3710/467019)
**Author:** [@Reach\_Adrian](https://forums.unrealengine.com/u/Reach_Adrian)\ **Replies:** 14\ **Last updated:** [August 20, 2022, 1:48pm UTC](https://forums.unrealengine.com/t/assertion-failed-asyncloading-cpp-line-3710/467019 "2022-08-20T13:48:57Z")
Hi everyone, This is really strange, getting the following error when I attempt to load a packaged build of our game: Assertion failed: Object-\>IsValidLowLevelFast() \[File:D:/Build/++UE4+Licensee/Sync/Engine/Source/… --- ## [Pixel Streaming Demo not working. Assertion Failed: Result == NV\_ENC\_SUCCESS](https://forums.unrealengine.com/t/pixel-streaming-demo-not-working-assertion-failed-result-nv-enc-success/470033)
**Author:** [@Charles\_HG](https://forums.unrealengine.com/u/Charles_HG)\ **Replies:** 3\ **Last updated:** [August 11, 2022, 2:45pm UTC](https://forums.unrealengine.com/t/pixel-streaming-demo-not-working-assertion-failed-result-nv-enc-success/470033 "2022-08-11T14:45:13Z")
Hi UE4 Answerhub, I’m trying to understand more about pixel streaming through the demo UE4 provide, however I’m receiving the error below when trying to open the modified shortcut of the .exe Assertion failed: Result =… --- ## [UnrealEditor keeps 4.26.2 keeps crashing on startup while loading assets, says "assertion failed"](https://forums.unrealengine.com/t/unrealeditor-keeps-4-26-2-keeps-crashing-on-startup-while-loading-assets-says-assertion-failed/490643)
**Author:** [@Question2005](https://forums.unrealengine.com/u/Question2005)\ **Replies:** 1\ **Last updated:** [August 8, 2022, 8:03am UTC](https://forums.unrealengine.com/t/unrealeditor-keeps-4-26-2-keeps-crashing-on-startup-while-loading-assets-says-assertion-failed/490643 "2022-08-08T08:03:27Z")
Im using the version of the unreal editor that is used for the Mechwarrior 5 mod editor, which is 4.26.2. For some reason, i am now constantly getting this crash after i start the editor. The editor starts fine and then… --- ## [When play level in editor: Error: Runnable thread TaskGraphThreadNP 0 crashed](https://forums.unrealengine.com/t/when-play-level-in-editor-error-runnable-thread-taskgraphthreadnp-0-crashed/379343)
**Author:** [@anonymous\_user\_6d350497](https://forums.unrealengine.com/u/anonymous_user_6d350497)\ **Replies:** 1\ **Last updated:** [August 1, 2022, 12:25am UTC](https://forums.unrealengine.com/t/when-play-level-in-editor-error-runnable-thread-taskgraphthreadnp-0-crashed/379343 "2022-08-01T00:25:36Z")
100% Crash when: Open project ContentExample Open level Animation Click Play in Toolbar \[2016.12.15-06.25.32:776\]\[633\]LogThreadingWindows:Error: Runnable thread TaskGraphThreadNP 0 crashed. \[2016.12.15-06.25.32:776\]\[… --- ## [Assertion failed on OnUnmountPak.Execute()](https://forums.unrealengine.com/t/assertion-failed-on-onunmountpak-execute/397628)
**Author:** [@wingedrobin](https://forums.unrealengine.com/u/wingedrobin)\ **Replies:** 3\ **Last updated:** [May 18, 2022, 8:36am UTC](https://forums.unrealengine.com/t/assertion-failed-on-onunmountpak-execute/397628 "2022-05-18T08:36:32Z")
Hi, I’m using FCoreDelegates::OnMountPak and FCoreDelegates::OnUnmountPak function to handle my patch/DLC pak file. But in ue 4.15, when i execute the FCoreDelegates::OnUnmountPak.Execute( ) to unmount the pak file. It … --- ## [Ue4.26.1 Assertion failed: launch to android device (Samsung galaxy on8 )](https://forums.unrealengine.com/t/ue4-26-1-assertion-failed-launch-to-android-device-samsung-galaxy-on8/480086)
**Author:** [@Ms\_PCBs](https://forums.unrealengine.com/u/Ms_PCBs)\ **Replies:** 2\ **Last updated:** [April 21, 2022, 11:33pm UTC](https://forums.unrealengine.com/t/ue4-26-1-assertion-failed-launch-to-android-device-samsung-galaxy-on8/480086 "2022-04-21T23:33:23Z")
LogPlayLevel: 03-11 06:00:17.122 24288 24358 D UE4 : Assertion failed: Index == 0 \[File:D:/Build/++UE4/Sync/Engine/Source/Runtime/OpenGLDrv/Public\\OpenGLES.h\] \[Line: 439\] LogPlayLevel: 03-11 06:00:17.122 24288 2… --- ## [Project crashes when transforming metahuman](https://forums.unrealengine.com/t/project-crashes-when-transforming-metahuman/489606)
**Author:** [@Micoosa](https://forums.unrealengine.com/u/Micoosa)\ **Replies:** 1\ **Last updated:** [April 4, 2022, 2:31pm UTC](https://forums.unrealengine.com/t/project-crashes-when-transforming-metahuman/489606 "2022-04-04T14:31:03Z")
Hi, I’m currently experiencing frequent crashing in UE4 while trying to move/rotate a MetaHuman character with retargetted Mixamo animations. Each time it crashes, this crash log comes up with the same failed assertion … --- ## [Packaging failed due to Assertion Failed ClassData](https://forums.unrealengine.com/t/packaging-failed-due-to-assertion-failed-classdata/498525)
**Author:** [@Capn\_C4ke](https://forums.unrealengine.com/u/Capn_C4ke)\ **Replies:** 0\ **Last updated:** [February 16, 2022, 12:48am UTC](https://forums.unrealengine.com/t/packaging-failed-due-to-assertion-failed-classdata/498525 "2022-02-16T00:48:11Z")
I’ve been trying to package my game but it keeps saying critical error. I was able to package it properly yesterday, and barely even touched anything today. I literally have no idea what’s going on, and I don’t have a re… --- ## [Assertion failed: Offset \>= 0 && BytesToRead \> 0](https://forums.unrealengine.com/t/assertion-failed-offset-0-bytestoread-0/476291)
**Author:** [@Pantoth](https://forums.unrealengine.com/u/Pantoth)\ **Replies:** 4\ **Last updated:** [December 6, 2021, 8:12am UTC](https://forums.unrealengine.com/t/assertion-failed-offset-0-bytestoread-0/476291 "2021-12-06T08:12:19Z")
Hi! I’ve a project in UE4.25 which works fine while playing in UE, but after packaging the game crashes at some point. The error-dialog appears, but the game itself is still playable. After a while the game closes. The… [Next page](https://forums.unrealengine.com/tag/assertion-failed/3974.md?match_all_tags=true&page=1&tags%5B%5D=assertion-failed)