Issue with 5.1 fresh install.

Development Getting Started & Setup
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Hi, we have encountered an issue where we cannot consistently launch a UE 5.1 without it crashing with errors. We can run the project without a problem on a couple of our dev machines. But the issue persists in 2 of our client PCs that we tested out.

We have tried

  1. Fresh epic launcher install → install UE 5.1.1 → launch and create empty project, works fine.
    Then, close and reopen the project crashes with the error:

Assertion failed: InHashSize > 0u && InHashSize <= 0x10000 [File:D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Containers\HashTable.h] [Line: 482]

  1. Tried opening an older project with errors as well. which is where we resorted to a fresh install of Epic + UE 5.1.

  2. Have tried driver updates/downgrades

  3. Tried wiping PC and reinstalling OS (Win11)

  4. Tried downgrading OS to win10

  5. among other small things

nothing yields luck. We wonder whether we are missing something small…

Any help in this regard is appreciated. do request for further info if needed. Thanks

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Hello there @Wasabi.in !

That’s quite a tricky scenario, as even fully wiping the affected PCs did not solve the problem. Which means, there’s an element that is reintroduced to the system, even after full format.

Now, the error you are getting, is tied to a HashTable conflict. Checking around the community, these are usually tied to data corruption, or rights conflicts. Since you fully cleared the system, and empty projects are working as intended, the engine’s cache should be fine. On the other hand, the older project may have carried over corruped data from the other systems.

So, the first step is to clear the old project’s cache. Open it’s directory, and delete folders DerivedDataCache, Intermediate, and Saved. Now, the next time you start the project, this will be re-generated. If this was the problem, it should be solved at this point.

But if the issue persists, then we have the other path, write permissions. Since these are client PCs, they most likely include extra security measures, which could affect the engine’s capacity to write and update the DDC. Please make sure these system have full rights for the project’s location, UE’s AppData folder, and the engine’s install directory. Additionally, consult if any security features could affect the functionality of the processes involved ( UnrealEditor.exe, ShaderCompileWorker.exe, etc).

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Hi @brs-sebascova, thanks for your quick response.

So, the first step is to clear the old project’s cache. Open it’s directory, and delete folders DerivedDataCache, Intermediate, and Saved

We have actually tried deleting all the project-specific cache (Intermediate, Binaries, DDC, Saved) in the beginning, and then regenerating them. That didn’t solve the issue either.

But currently, we are trying to launch 5.1 on Windows 10, a fresh install. All I did after installing Epic Launcher (and installing UE 5.1) was launch the engine and create a blank project. I saved it and quit. When I reopen the project, it crashes. When I now launch UE5.1, that also crashes..

Both are pointing to the same hashtable error:

`Assertion failed: InHashSize > 0u && InHashSize <= 0x10000 [File:D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Containers\HashTable.h] [Line: 482]`

empty projects are working as intended

However, I should note that the sample project does open sometimes, but not always. Additionally, the original project is not present on this computer, so that couldn’t have caused the corruption this time.

Since these are client PCs, they most likely include extra security measures

We originally set up these client PCs, so there shouldn’t be any security limitations either. In case you know of a way to get rid of such limitations, if they somehow exist, do let us know. FYI, we have tried the verify button on the Launcher’s options.