I can work around this particular issue by introducing a "universal joint" https://en.wikipedia.org/wiki/Universal_joint that should behave much better than two hinge joints. Also better for performances.But it's of course a big problem that players making reasonable use of existing parts can completely break the game. And yet I have no solution. To my knowledge, all physics engine are sensitive things that are quite easy to break... The kind of issue that can ruin the fun π