I have a simple setup with some spawners spawning cubes with default physics values and no children (see this thread for more details). I get a hash of the state at every 'physics Tick' and write this hash to file to compare later. It all works fine with restitution value of 0 (tested to 5000 ticks), but when I use a higher value (tried 0.5 & 0.8) determinism breaks when the amount of 'physics ticks' in a frame is different from the original run. So if I just let it run the FPS will be >200 resulting in 1 physics tick per frame. And a rerun is equivalent (saved file hash is equal, so all bits are equal of the Translation, Rotation and PhysicsVelocity). But when I slow down the simulation before the fixedstepsystemgroup multiple steps will be taken to catch up to the real time and determinism breaks. I don't understand why the fixedStep catch up running the FixedStepSimulationGroup 3 times would result in a different result as running 3 frames with each 1 'physics tick'. What am i missing here? Is there a way to not have this issue? I am tempted to write my own catchup code and manually try to trigger a physics step... but it feels like a rabbit hole that might not even fix the issue or just lead to the next issue.