@garapoes this is a problem we reported here (# 31), but the issue is that thus far, we haven't found a way to be able to reproduce it so that the developers could see the bug in action. Many times, the black window will be normal the next time you load the lot or save, and it also doesn't seem to transfer as a black window to the gallery. You can also delete the window and replace it with a new one, which many times prevents at least that window from turning black. I had a build with tons of windows, and nearly every time I loaded my game, at least one was black. I would just delete and replace and move on...annoying, I know. :P
Comments
Try coming completely out of the game.
Repair the game.
Delete the cache files
https://sims4.crinrict.com/en/2014/09/delete-cache-files/
Then load the game and see if the issues remain.
http://forums.thesims.com/en_US/discussion/817478/hello-come-and-introduce-yourself
http://tinyurl.com/OneRoomOneWeek
http://tinyurl.com/rosemow
My Showcase thread https://forums.thesims.com/en_US/discussion/948861/rosemow-s-rooms-showcase
I just ignore it and it goes away on its own