I'm running into a problem where copy-pasting a keyframe on the timeline results in a weird duplication issue
there appear to be two "Rotate" timelines for the same bone. They conflict, and the animation will pop. I typically have to delete my pasted key and try again until it works.
I don't have a 100% repro case, but it has happened several times since upgrading to 1.7.02
See the attached image.