I am working on a train for my game and i realised that it just breaks completely by adding tons of force for some reason. Here is the train without players
And here is the train with players
From what is printed I can see that the velocity of the train is way higher than it should be, despite the fact that the calculations for velocity don’t involve the player in any way.
When in doubt with physics blame Physics Network Ownership. Try setting the network ownership to the server and making the player massless.
Also Roblox physics regarding collisions with the track are just very buggy in general not sure what the conditions are, it might also be best to find a different method like using AlignPosition to a tweening part for maximum reliability.