Simulate physics for industrial mechanisms

I’m currently trying to find a way to physically simulate mechanisms for industrial purposes (those mechanisms are modeled by engineers).
Those mechanisms have a lot of constraints and can be composed of tiny pieces.

Here is an example of simple mechanism:

I tried to use PhysicalConstraint to simulate this simple mechanism but there are lots of instabilities which completely broke up the whole thing (the physics engine tries to solve all those constraints but the simulation seems to produce more and more instability which leads to more and more tremors until everything fall appart).

I tried to solve those instabilities by several ways (scale the whole mechanism, set the same mass to all pieces, for a given constraint tweak which piece simulates the physics, etc,), but it seems there is no way to properly simulates it.
It seems that internal collisions make the simulation unstable.

Do you think that I should code my own simulation or there is another way to solve my problem (if I have to code it I don’t know what to do because everything I need is physics and I don’t think that I will do a better job than PhysiX) ?