UMG jittery rotation

Seems like a simple thing: rotate an image in an overlay container! (I have also tried this in a size container. No dice.)

Here’s the simple UMG code:

And here’s what happens: https://dl.dropboxusercontent.com/u/3299208/JitteryRotate.gif

Can’t seem to get rid of it, no matter what I do.

Any ideas here? I’m super confused.