UE4 Crashes on build all

When I press build all, as soon as it gets to the lighting it crashes the PC.

When it reaches the lighting section it crashes. Worked previously, no advanced lighting only 4 static lights in the whole level

Hi Stephie-san,

Can you provide the following information:

  • When you get a crash is it the whole editor that is crashing or just lightmass?
  • If it’s the editor and you get the crash reporter window I’ll need your full call stack from the crash reporter window, your Epic/Machine IDs, and the logs that can be found in Project Folder > Saved > Logs.
  • If it’s Lightmass I’ll need to know what the error was from window that pops up inside the editor. A screenshot can work for this.
  • Have you tried this on 4.10/4.11? There is about 6 months of development between these 4.9 and 4.11 with some significant changes that may have already been resolved.
  • Do you have any repro steps that can cause this to happen 100%?
  • Does this happen in your current project or a new blank project as well?

Thank you!


Hello Tim,

The whole editor crashes - I will forward the logs

I haven’t tried on the newer versions as the project is in the original and I don’t want to loose anything.

When I press build it crashes each time, This is the only specific action that causes it to crash

I have not tested it against other projects yet. I shall forward with the logs


Hey guys, I’m facing a similar issue. PC crashes when i click on Build All. Its not specific to any particular section. Sometimes it lighting, sometimes its geometry, or anything.
Using version 4.18. I don’t think its generating logs for this crash either. Although, when i start PC and load the project again, it asks if i want to restore. Please help me fix this.