2 weeks ago i was working on one of my levels, and every thing was OK…
Yesterday; in the same project I did the following:
created a new level from the same level I was working on (using save as…)
imported new assets to the (Content Browser)
delete all the old meshes in the (Scene Outliner)
used the new assets in the 3D viewport Editor, fixed the materials… build lighting… and everything was OK
Today; I went back to the old level mentioned above and tried to build it’s lighting again several times; but unfortunately it didn’t work and UE4 Editor crashed each time…
Note: This project contains 7 levels… in all the rest 6 levels I was able to build lighting; except this one …!!?
I did search here in the (Answerhub) for similar issue… found one; advising to delete three temp folders in the project (Saved, Intermediate, DerivedDataCache) and run UE4 again… but this try didn’t fix the crash problem…!!?
It sounds like one of the lights in the level may have become corrupted. We are unsure of what causes this but the fix is to delete and recreate all of the lights in that level. Give that a try and see if it will build correctly.