@kaisa.s.blue.apple
Your post reminded me something that I had to share and ask...
But first, in order to see curves in Curve Editor you have to sample your clip. Now at this point I had to say "Sample Optimized". But now I hesitate...
I hope someone with extensive Mocap experience would help you more, but briefly only smoothing is not the answer and can make your clip even worth than it is.
Now the question. I noticed this a few days ago when was helping someone. Am I loosing my mind, or have I not seen that before, or is it a bug introduced in IC 7.9??
When you Sample Optimized, the clip is now getting messed up. Sampling Optimized is basically introduces sliding and jerky movements which were not in the original clip.
Moreover if you flatten it afterwards, those are hard-coded into the clip. Just look at the video. Is anyone noticed that? Is it reproducible? I used Heidi Twirl Hair clip.
Note: sampling per frame shows no sing of a problem as it should not.