The one thing not asked was if the same issue happened if you excluded it from WB. This would narrow down the issue.
I will check, but that would still be unacceptable.
It is a known thing that you will not get some animations with universal apps, I assume your Skype hasn't been 'upgraded' (and I use that term loosely) to a universal version.
Both the Skype app, which animated fine a week ago, and the Desktop version of Skype exhibit the same lack of animation.
If I run Curtains rather than WindowBlinds, animations happen. When I say animations, I am speaking of wobbly windows. Movement animations.