First of all, I must admit to NOT being an expert whatsoever. Having said that, here are my thoughts/observations.
I stepped through the jittery clip, frame by frame, and what I’m seeing is that every frame is repeated (i.e. 50% speed change with no frame blending). You might want to try to open a copy of that particular clip in Cinema Tools and conform it to 23.98 to see what it looks like then.
Good luck!