@Rflong7
Thank you for that info! However, the issue doesn't seem to be connected to layers as it happens also when I don't use layers.
I discovered that the lightning issue only arises with bottoms that have bump (normal) maps. As you can see in the picture I posted at the beginning, it works with one skirt whereas with the other skirt it looks buggy. The skirt where it works doesn't have a bump (normal) map, the other one does.
So an imported top without normal maps works with bottoms both with and without normal maps.
But an imported top with normal maps only works with a bottom without normal maps but not with a bottom with normal maps.
https://i.imgur.com/8wXnmq8.png
Here, the first row shows the files of a skirt that works, the second row the files of a skirt that doesn't work.
So it seems the root of the problem are those normal maps and that they somehow conflict. I wish there was a way to just delete or disable all of them. :/
