[UE 5.8.3 HotFix Bug)

General Issues and Bug Reporting (Unreal Engine)
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Summary

[5.8.3] Abnormal RAM usage + UE freeze for more than a minute + fault report from the diagnostic service

What Type of Bug are you experiencing?

Foundation (C++ Tools, Profiling, & Pipeline)

Steps to Reproduce

Hello,
I have been developing on version 5.8.2 for a few months. I am currently creating a multiplayer game via Steam.
I was running tests just yesterday, and everything went smoothly when launching maps or the game.
Today, I updated to version 5.8.3.

  1. Since then, when I launch the game from Unreal in PIE/2-player/listen server mode, the game runs extremely sluggishly.
  2. I get a message stating that I do not have enough memory. I currently have 35 GB of DDR5 RAM. That is a decent amount; everything worked perfectly on version 5.8.2.
  3. It is evident that my memory is completely maxed out, whereas this was not the case before.
  4. When I exit the game, the entire Unreal editor freezes and becomes unresponsive. After waiting one or two minutes, I can interact with the software again, but the RAM remains maxed out. There is heavy data exchange with the SSD.
  5. It is impossible to continue working; the software has become unstable and frequently lags.
    Below are the diagnostics from the editor. I never encountered this issue with version 5.8.2.
    I have restarted the computer, but the problem recurs every time I launch the game within the editor.

Expected Result

Normal launch, smooth performance, game fully functional

Observed Result

memory is completely maxed

Affects Versions

5.8

Platform(s)

Windows

For crash reports, include your callstack

Engine Version: 5.8.3-58210709+++UE5+Release-5.8
Stall Detector: FEngineLoop::Tick
Stall Duration: 4.921725
Stall Time: 2026.09.22-18.52.22

StackTrace

00: [0x00007FFD47BB2A45] [UnrealEditor-Core.dll] : : <>:0
01: [0x00007FFD47BC8AD3] [UnrealEditor-Core.dll] : : <>:0
02: [0x00007FFD47BB3983] [UnrealEditor-Core.dll] : : <>:0
03: [0x00007FFD47B84343] [UnrealEditor-Core.dll] : : <>:0
04: [0x00007FFD47BA2757] [UnrealEditor-Core.dll] : : <>:0
05: [0x00007FFD4029F3CA] [UnrealEditor-SlateCore.dll] : : <>:0
06: [0x00007FFD40874A9B] [UnrealEditor-Slate.dll] : : <>:0
07: [0x00007FFD4086C73A] [UnrealEditor-Slate.dll] : : <>:0
08: [0x00007FFD40908805] [UnrealEditor-Slate.dll] : : <>:0
09: [0x00007FFD408F5ECC] [UnrealEditor-Slate.dll] : : <>:0
10: [0x00007FFD40A13C04] [UnrealEditor-Slate.dll] : : <>:0
11: [0x00007FFD40A121C8] [UnrealEditor-Slate.dll] : : <>:0
12: [0x00007FFD409B924F] [UnrealEditor-Slate.dll] : : <>:0
13: [0x00007FFD409EF8A6] [UnrealEditor-Slate.dll] : : <>:0
14: [0x00007FFD40A1E009] [UnrealEditor-Slate.dll] : : <>:0
15: [0x00007FFD228AEE90] [UnrealEditor-EditorPerformance.dll] : : <>:0
16: [0x00007FFD22892CC2] [UnrealEditor-EditorPerformance.dll] : : <>:0
17: [0x00007FFD40B369EB] [UnrealEditor-Slate.dll] : : <>:0
18: [0x00007FFD40B72A43] [UnrealEditor-Slate.dll] : : <>:0
19: [0x00007FFD40871A8A] [UnrealEditor-Slate.dll] : : <>:0
20: [0x00007FFD408BA75E] [UnrealEditor-Slate.dll] : : <>:0
21: [0x00007FFD408ACA1F] [UnrealEditor-Slate.dll] : : <>:0
22: [0x00007FFD408A453E] [UnrealEditor-Slate.dll] : : <>:0
23: [0x00007FFD40FD3323] [UnrealEditor-ApplicationCore.dll] : : <>:0
24: [0x00007FFD40FBE9EA] [UnrealEditor-ApplicationCore.dll] : : <>:0
25: [0x00007FFD40FD68E1] [UnrealEditor-ApplicationCore.dll] : : <>:0
26: [0x00007FFD40FBAC61] [UnrealEditor-ApplicationCore.dll] : : <>:0
27: [0x00007FFE545252C6] [USER32.dll] : : <>:0
28: [0x00007FFE54525D9D] [USER32.dll] : : <>:0
29: [0x00007FFD41007279] [UnrealEditor-ApplicationCore.dll] : : <>:0
30: [0x00007FF708542175] [UnrealEditor.exe] : : <>:0

Engine Version: 5.8.3-58210709+++UE5+Release-5.8
Stall Detector: FEngineLoop::Tick
Stall Duration: 349.512665
Stall Time: 2026.09.22-18.46.27

StackTrace

00: [0x00007FFE56444A14] [ntdll.dll] : : <>:0
01: [0x00007FFE56382ECB] [ntdll.dll] : : <>:0
02: [0x00007FFE5631941D] [ntdll.dll] : : <>:0
03: [0x00007FFD47A3FD5D] [UnrealEditor-Core.dll] : : <>:0
04: [0x00007FFD43D4EE79] [UnrealEditor-Engine.dll] : : <>:0
05: [0x00007FFD43D56DF5] [UnrealEditor-Engine.dll] : : <>:0
06: [0x00007FFD4661D40D] [UnrealEditor-CoreUObject.dll] : : <>:0
07: [0x00007FFD466640A6] [UnrealEditor-CoreUObject.dll] : : <>:0
08: [0x00007FFD46664501] [UnrealEditor-CoreUObject.dll] : : <>:0
09: [0x00007FFD465E8043] [UnrealEditor-CoreUObject.dll] : : <>:0
10: [0x00007FFD4666CA3A] [UnrealEditor-CoreUObject.dll] : : <>:0
11: [0x00007FFD46617D3B] [UnrealEditor-CoreUObject.dll] : : <>:0
12: [0x00007FFD3E6185D4] [UnrealEditor-UnrealEd.dll] : : <>:0
13: [0x00007FFD3DF9E00F] [UnrealEditor-UnrealEd.dll] : : <>:0
14: [0x00007FFD3EB07696] [UnrealEditor-UnrealEd.dll] : : <>:0
15: [0x00007FF708542779] [UnrealEditor.exe] : : <>:0
16: [0x00007FF70852C4AC] [UnrealEditor.exe] : : <>:0
17: [0x00007FF70852C5BA] [UnrealEditor.exe] : : <>:0
18: [0x00007FF708531256] [UnrealEditor.exe] : : <>:0
19: [0x00007FF708545C74] [UnrealEditor.exe] : : <>:0
20: [0x00007FF70854902A] [UnrealEditor.exe] : : <>:0
21: [0x00007FFE5435CD87] [KERNEL32.DLL] : : <>:0

2 
Hello,
I would like to confirm and add some details to what I said earlier:
As long as I am in the editor, everything works "normally."
When I run tests in PIE/2-player/listen server mode, things go fine on the first map (the main menu).
When the host starts the game and loads the new map, everything is okay; RAM usage increases slightly, but within very reasonable limits.
The spike in memory consumption occurs the moment the client player joins the ongoing game (Steam session). That is when things escalate: RAM usage climbs steadily for no apparent reason—increasing by about 100 MB per second. It becomes impossible to even exit the game properly (using the in-game function); everything freezes. Memory usage keeps rising until it hits the limit. The system slows to a crawl and stops responding, eventually resulting in an error message from UE as part of the diagnostic process.
I use translator from french
3 
Hello,
I am getting back to you after investigating my project.
I would like to apologize to Epic Games regarding my previous suggestions: the issue did not stem from the UE5 update; rather, I had enabled replication for a master file with many child instances, which caused network communication demands to skyrocket. Everything returned to normal once I disabled that replication. Sorry for the inconvenience.
4

Same issue on my end. Went from 5.7 to 5.8.3 and Max Memory, Unreal freezing, Crashing max Virtual Memory, Max SSD C drive, unable to do anything. I have a huge world, thou just a section loaded and everything was maxed out.

Worked with GPT for many days, doing Insights, process of elimination.

Issue was with Road Landscape Splines. This was using 40 GB of memory, and 180 GB virtual memory, and crashing.

When I set all the Road Landscape Splines to Is Editor true, everything runs perfectly fine.

Some sort of issue, this is what GPT says.

Then I’d give Epic something close to this:

Summary
In a large World Partition landscape, enabling LandscapeSplineActors in PIE causes extreme memory allocation and paging. Physical RAM rises to approximately 61–63 GB on a 64 GB system, committed memory has reached approximately 168–225+ GB, and the Windows pagefile SSD becomes saturated.

The issue is reproducible even after disabling collision on all Landscape Spline control points and segments and disabling/removing a separate Blueprint road-generation system.

Marking the LandscapeSplineActors Is Editor Only Actor immediately eliminates the behavior. With the same map, Road Creator and player running, memory remains approximately 27–30 GB physical and ~73 GB committed, with little/no SSD paging.

Engine
Unreal Engine 5.8.3
Build: 5.8.3-58210709
Windows 11

Project configuration
Large World Partition landscape using LandscapeStreamingProxies and many LandscapeSplineActors for road/terrain deformation.

Memory Insights evidence
A controlled Memory Insights trace comparing pre-PIE to high-memory PIE showed approximately 44 GiB allocation growth.

Approximately 41.3 GiB was tagged Physics.

Approximately 18.2 GiB was ChaosTrimesh.

Resolved allocation call stacks repeatedly include:

UBodySetup::PostLoad
UBodySetup::TryGetCookedData
UBodySetup::CreatePhysicsMeshes
Chaos::FTriangleMeshImplicitObject::SerializeImp
Chaos::FTriangleMeshBVH::Serialize

The allocations occur during async loading / UWorld::FlushAsyncLoading / PIE startup.

Reproduction / A-B test

  1. Open World Partition landscape containing LandscapeSplineActors.
  2. Allow LandscapeSplineActors to participate normally in PIE.
  3. Start PIE.
  4. Physical memory rises toward the 64 GB system limit and Windows begins heavy paging.
  5. Stop PIE.
  6. Select the LandscapeSplineActors and enable Is Editor Only Actor.
  7. Restart/retest PIE with otherwise equivalent content.
  8. PIE runs normally at approximately 27–30 GB physical RAM with little/no disk paging.
  9. Disable Is Editor Only Actor, but set Landscape Spline points and segments to No Collision.
  10. Retest: memory again rises toward the system limit.

Expected
LandscapeSplineActors should stream appropriately with World Partition and should not cause tens/hundreds of gigabytes of additional committed memory during PIE.

Observed
Merely allowing LandscapeSplineActors to participate in PIE causes extreme memory growth. Disabling spline collision does not resolve it; excluding the LandscapeSplineActors from PIE does.

Regression information
This project was usable under UE 5.7. The severe PIE memory behavior appeared after moving to UE 5.8.

I’d include your before/after Task Manager screenshots. The pair is compelling:

Landscape Splines runtime: ~61–63 GB RAM, paging/SSD saturation.

Landscape Splines Editor Only: ~29 GB RAM, 34.7 GB available, C: ~9% in this shot.

And absolutely mention that you’ve already captured a Memory Insights .utrace with symbols. If their forum allows attaching it and it’s not enormous, attach it; otherwise say it’s available. Your trace showing Physics → ChaosTrimesh → UBodySetup is much more useful to an Epic engineer than Task Manager alone.