Hello there! Who knows, perhaps there is an answer to be found here someday.
The following keeps happening to me when I add 4-5 textures to an area:
I can’t retexture this nor does it ever load. This gets extremely frrustrating as I have to delete the area, re-insert a flat one and remodel/retexture the entire part.
I encountered this bug in earlier engine versions as well. I hope this gets fixed soon, because it really hinders any progress.
What you are encountering is a limitation within the SM3 shader model which only allows 4 textures per component (including your non-weighted blend layers).
Let me know if you have further questions or need additional assistance.