Hello, is UE-35999 somehow related to the originally described issue above that when placing / copying a BSP, then several BSP surfaces lose their material? I have this issue in my new 4.13 project so whenever I copy (Alt+drag) or insert a BSP, then several (I think always the same) BSP surfaces lose their material.
Anyway, going from 4.12.5 to 4.13 created a load of BSP issues - not necessary new ones but their impact is heavier (e.g., BSP Order).