Issue with Tween Playback on Skinned Meshes

I’ve encountered an issue with skinned animation playback which I can’t seem to wrap my head around. I’ve noticed that, for some of the models I’ve imported, when attempting to animate them, the skinned geometry jitters as it follows the moving bones.

This hasn’t been an issue previously, but when I was testing out animations on one (previously perfectly functional) model, suddenly these problems appeared. More perplexingly, as I went through my storage file, I noticed that while some models were affected, others were also exempted. Best example is the linked recording, whereupon two models which I’m fairly sure are completely identical, are disparately affected by the issue.

A little bit of background - I’m using a custom-built animation process which uses tweenservice calls for the bones. Hasn’t given me any issues (past bugfixing) until now, and it appears the bones underneath animate smoothly, just the skin on top jittering behind. In some cases, separate meshes in the same models are intermittently affected and unaffected. Does anyone know what could be causing this/an easier solution than reimporting?