This is a an effect which has got significantly worse since r79. It happened a little on r77 but was manageable.
I'm creating a pendulum beneath a spaceship using revolutes
The capx is here:-
Use the mouse to get the ship to move around. The animation has to change when the ship reverses to make sure it stays up the right way. When the frame changes, the revolute origin (connection point) moves slowly away from where is should be with each change.
Also getting "stretching" if the object connected is too dense and this could be the physics catching up, but the weird moving of the origin is definitely a calculation inaccuracy (a bug) as it wasn't present in r77.
Tried to force the chain back to the origin, but got an epic fail when I tried... As my current game relies on fun with joints would be great to see if this could be fixed. I know the animation change is making it worse, but I have to change frames.
[Using Chrome on 64bit C2]