EDIT: Keeping the post here if needed for future reference, but this issue was discussed and patched. See this thread: Adaptive Physics Breaking Game
Earlier today we’ve received reports that our games had collision issues with their projectiles. It seems that when a fast-moving projectile tries to collide with an unanchored part, the collision frequently fails at the start of the projectile’s trajectory. We’ve come to the conclusion that the Adaptive Timestepping is currently causing the issue, as setting the PhysicsSteppingMethod to “Fixed” resolves this entirely. Here’s a place that reproduces the issue:
collisions_timestepping.rbxl (45.4 KB)
And two videos that showcase trying to have two parts collide at moderately high speed (the red projectile spawns 5 studs before the black one).
PhysicsSteppingMethod = Adaptive (fails most of the time, though not always)
PhysicsSteppingMethod = Fixed (never fails)
While it is expected that adaptive timestepping may lead to less accurate physics simulations, this issue has only been reported starting today. If Fixed Timestepping was not an option, this could have turned critical for our games.