Can't close editor or save lightmaps on one map


Since Unreal Engine 4.16 (although that might have just aligned with a major change in the level) I’ve been having some pretty odd issues with lightmaps. The level has thousands (~4000) of lightmapped objects, ranging from 64x64 to 512x512. At first, Unreal Engine complained about Battle_CrossStreams_BuildData.uasset not being able to be saved. That error went away when I backed off on lightmap resolution of several objects.

Now it builds and saves, but, when I attempt to close the editor, it just doesn’t close. It doesn’t freeze either… it’s like I just never clicked the close button. Today I noticed that my Output log was also getting spammed with “Cmd: CLOSE_SLATE_MAINFRAME”. It seems like the editor only fails to shutdown after I do a lighting build.

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Also, when I re-open the editor (or package the game and run the packaged game) it complains about lightmaps not being built, so I’m guessing that it never actually saved, even though the save appears to have completed without error.

I’m not too concerned about this issue, because I need to replace a lot of the map anyway to reduce draw calls for VR, but I’m wondering if there’s any, like, upper limit of lightmap numbers (or whatever) I’m hitting. Again, it seems to have started after migrating from Unreal Engine 4.15 to 4.16, but that could be co-incidence. The other maps seem fine, too.