When you are making sceneries, be sure to give every texture a unique name that can be associated with your project only!
I had a problem where the textures on a hangar in one of my sceneries were screwed up after SU5. It turned out that my texture was named “hangar1.png” and that at least three other add-ons in my Community folder had textures with the same name. I renamed the texture to ICAOCODE_hangar1.png, re-built the scenery and the problem was gone for my scenery…
So it seems that MSFS loads only one texture if there are several with the same name and applies it everywhere where that name has been used. Even though they belong to different add-ons! Not good, and something that need to be fixed by Asobo.