Hello I have got a big problem and dont find an answer…
If I drop a normal material on a BSP Box the material turns after about a minute into random stripes withe the colour of the material i droped on…
I am building a house and its just on some of teh walls …PLEASE HELP
Thanks 
ich bin deutsch also auch gern deutsche antworten
Does it happen when after you built your light? + which engine version do you use?
nop i dont do anything … just work on other walls but i guess thats not the reason.
the latest one
the material looks completely different its not about the lightning
So it just happens randomly (because in 4.7 there was a bug which turned the material into “stripes” after you built the light)? What happens when you set the alignment to something else (in the details panel of your bsp brush under geometry). So you use 4.8 preview? (or the latest stable one) 
4.7.4
hab ich schon gemacht aber hält auch nur einen augenblick
Hmm, could you probably post a video which shows the problem? Which kind of material do you use? (try one from the starter content). What are you exact steps so that I can try to recreate it. Also make sure to post a pic of the end result
Ok, I checked your map and it seems like it’s a bug. Whenever you move the bsp brush it will reset the uv’s, because it’s rebuilding it.
workaround:
-move and adjust everything so that it’s in the final position -> after that do the part with the alignment and dont move the bsp anymore
-mostly this problem appears when you scale your brush instead of using the bps editing mode
-you could just replace those bsp parts with new brushes