Not sure what exactly causes this bug but it happens after changing appearance a few times and having saved item sets. The character in the transmog window gets darkened/faded out like the background. Have tried numerous things to fix it without success

I have no idea how to fix that, but I also got this with other transmog-addOns, not sure if it is a blizzard-bug maybe.

I've gotten this with multiple transmog addons. I may be wrong but I think I've seen it without any as well.

Reloading fixes it.