AFAIK the supply, pulldown and take up should be near on continuous shouldn't they? No jerking. Is the supply reel over-running, leading to a small surplus of film that is 'used' then the claw has to start the reel moving again from scratch every so often, causing a jerk? I'd have thought a slight bit of back tension on the supply would be desirable.
there's a eumig on youtube with what I assume is an exaggerated effect of what you might have?
https://www.youtube.com/watch?v=kKjkBvzB32o
PS, dont want to insult you but I assume it's threaded properly....some early projectors need a manual loop at the top and bottom of the gate in between the sprockets and the gate to isolate the gate from the reels, as it were. Later ones form the loop automatically.