Hey everyone,
i'm starting my first animation, something small and i'm having some problems.

I've created a character and it has a rigid binding with a few flexors. The weird thing is that, my flexor does this flip kind of thing which distorts my geometry. I've attached two photos, where from one frame(frame139) it's normal, and then in frame 140 the flexor flips. But it goes back to normal like 5 fames later.

What am i doing wrong?