I am having similar issue. I am guessing this is happening because Sketchup is not good with UV Mapping (I am not sure if sketchup texture mapping is even related to lightUV Mapping) and some meshes imported to Unreal get their LightMap generated by unreal and dont turn out good. Nevertheless was anyone here successful in finding a good fast solution to bypassing this? I have been struggling for 2 week. I have tried deleting the UV Map 1 and regenerating it, sometimes it works and sometimes it won’t, i have realised that the squares are like stamped into the lights in the level that cast onto the surface because i tried deleting the lights and adding new ones and that solved it sometimes but with generating a new lightuv map to the surface. There should be an easy way to bypass it i just cant figure out how yet.