I find problems in the Blender physics engine even in simulating simple fall of a sphere. I probably have done some setup wrong because i've also tried bullet engine stand-alone and it works better.
This is the experiment setup:
sphere positioned in (0,0,0) with mass 1 kg
gravity set to (0,0,-10 m/s^2)
no friction, no bounciness, no damping
steps per seconds and solver iteration set to 1000
I thought that there were a constant friction somewhere but i calulated the second derivative to get the acceleration and it's not constant at -10 m/s^2!
i've had to put my animation start from frame 0 instead of 1. Also in Rigid body cache in Scene setting.