Lighting build crash when foliage and toggleable lights in same map

I get this error when I try building lighting. I think it happens when I have foliage and toggleable lights in the same map. Have any of you run into this problem? How did you solve it?

[0565.32] Critical: appError called: Assertion failed: InstanceMapping.ShadowmapTexture == NULL [File:D:\ ... path ... \Development\Src\Engine\Src\UnShadowMap.cpp] [Line: 967]

Stack: appFailAssertFunc() Address = 0xfa80dc79 (filename not found) [in D:\ ... path ... \Binaries\Win64\RPGTacGame.exe]

I’ve been really careful with my lightmap resolutions. My grass cards have just 1x1 or 2x2 lightmaps. Most of my rocks and small plants are no more than 8x8.

OK, I think I’m able to get around the issue by making them movable lights instead of toggleable. As movable lights, they don’t get included in the lighting build. But they come at increased runtime cost. I think so long as I use them sparingly, I should be fine.