Whole ragdoll jitters when no forces acting on it, but responds normally otherwise

I've got a ragdoll style armature (with character joints connecting all the capsule colliders), and the ragdoll physics look nice when they are being acted on by outside forces. However, when left to their own devices, the whole ragdoll jitters as one. It will clip through mesh colliders substantially, as if jittering around some central position.

I've tried various things like changing interpolation mode for all rigidbodies, increasing drag on them, changes their masses, and also of course changing the physics settings for the project, but nothing seems to stop this. Anyone aware of a cause?