When I make Rigid Body 6DOF constraints through the Blender UI, any hard force on a constrained object will knock it out of the constraint slightly for a moment, and it will bounce back into place quickly. This does not happen through the bge.constraints.createConstraint method. How can this be controlled?
I also tested it out using joints in the blender dynamics tools.
It not only works the way I need it to in the game engine, but it includes things like “break joint” which aren’t in bge.
Have you tried increasing the substeps value in the world panels?
I believe since Blender moved to the latest version of Bullet, the engine now defaults to a less precise simulation than it used to, something which can be restored a bit by increasing the mentioned value.