I read your part about applying skin to a fresh build and you couldn't reproduce it, so I thought, what if a skin setting is not read correctly and needs to be written in a new way by the application. I toggled random skin Config options and relaunched WACUP - the playlist shows correctly again. Easy fix, haha.
And your last text block about the whole window frame going blank, yes, that's an issue too I've observed for a long time, just never bothered to report.
There's one more issue that appeared with a recent update, but I ain't reporting it yet, unless I see it happen one more time.