I found the solution in case anyone else has this problem:

This happened to me when I tried to make adjustments to the existing movements, for some reason the entire video would not play. I had to open up a backup file and add new movements instead of editing the existing ones.

I know this isn't a real solution, since I should be able to edit my existing movements, seems that my SU file is corrupt? And this is the only way around it.

Hello,

My animator clip editor seems to not play when movements are toggled, but when I toggle them off, it plays perfectly fine - except I need the movements in the video as well. I've played the animation through the editor before and it's always been fine, however now it seems to not be working at all.

Can anyone help me with this?