It seems that roblox physics is not working on moving platforms. This was working fine last week and nothing has changed with the game since it is broken.
Players can’t stand on a moving platform (roblox physics). They just slide off.
After some hours of trial and error I have been able to reproduce this issue.
The problem is when there is a cancollide Union either moving or welded to the Roblox physics moving part. When the union(with depth, for example part of the union in Z axis) is moving the character cannot stand on it or any part that is near it that is also moving with the assembly, it will move under the character and the character will slide off.
In Studio the player can stand on the Union as expected. this only happens in live games on the client.