Chaos twitches. Nothing you can do about it really.
Either swap to PhysX by building the engine from source, or (and you should either way) put the ragdoll to sleep immidiately.
Bt put to sleep, maybe you actually want to go really aggressive on it rather than rely on Epic, or Chaos…
Save a pose snapshot of the animation. Use the saved pose as the animation. Disable any simulation and everything else entierly.
You can do this aggressive enough that it just triggers the moment the whole physics body collapses, or you can ease it to where it awaits for the body to be put to sleep by the engine settings.
Because you are dealing with boneheads who can’t code, apparently, I truly suggest you save yourself from issues by going the extreme route about it.
Being it is a simulation, if you stop it in its tracks too fast it won’t look good.
So, what you can do is test the position of the pelvis, and headbone for stability.
Once 3 to 4 frames have returned very similar values within say .001 UU from each other, you can go ahead and toggle the pose snapshot system.
Goodbye problems.
Ps: with physx, you are still supposed to swap from a simulation to a pose snapshot - the difference is you do not need to run your own tests and you do get a callback when the body is put to sleep…