Waitmutex exited with code 6 (MSB3037)

for me it was I deleted a plugin from the engine and using it in my project

For me it was trying to build it in Visual Studio instead using the Live Coding way, Ctrl+Alt+F11

If you had opened Unreal Editor Plz Close And Try Again Maybe Work.

I have a same problem. Do you resolve this error???

I found out that in my case it was related to a plugin “AccuRig”. When it is activated it generates this error. I deactivated the Plugin and now ue / Lyra is working.

Change in LyraStarterGame.uproject the following lines:
image
from True to false.

This resolved my issue, maybe your issue is related to same plugin or other. Check LyraStarterGame.ueproject which plugin are activated /deactivated. I would deactivate all thirdparty plugins.

Hope it solves for you, kind regards,
Ivan

Hey I know its been a year but im following the same tutorial you are and have the same error, did you ever find a fix?

Close all the running instance of Unreal, search in task manager if any instance is running and close it then go to visual studio and build the project.

Try using cmd prompt to see more details about the error

Run Build.bat Manually

You can manually run the command to gain more information about the error:

  1. Open a Command Prompt.
  2. Run the command from the error message:
  3. “E:\Program Files (x86)\UE_5.3\Engine\Build\BatchFiles\Build.bat” Vr_Game_CPPEditor Win64 Development -Project=“G:\Game_CPP\Game_CPP.uproject” -WaitMutex -FromMsBuild
  4. See what the error says, it can be a misspelling or something else.
1 Like

Thanks, this helped me pin down what was causing my build to fail with this error. Upgrading a project from 4.27 to 5.3, one of my lines was using Hit.Actor, where Hit.GetActor() is now needed instead. I wouldn’t have guessed that running the .bat manually would offer more context.

Rather annoying that it gives such a vague error in the first place.