Bodies linked with a Rigid Body Joint are detaching by itself in simulation I have two rigid bodies (they both are small hierarchies actually) and attached them to each other using a 6dof joint with all limits locked to zeroes.

One of the bodies is controllable with left-right keys, there is a motion actuator that does simple rotation.

I start a simulation, do the rotation, wait 5-10 seconds, and the joint detaches by itself. The second body stands still in the air. 



The scene file is here download blender scene
Ok, I found it. I had to set "No Sleeping" flag in the Physics properties for each of the rigid bodies.