As a developer, it’s impossible to reliably create WeldConstraints attached to moving bodies on the server. Because of latency, the offset on the server/client end up being different:
It seems this happens because WeldConstraints are simulated disjointly on the server/clients. They each calculate their own offsets between Part0/Part1. This makes WeldConstraints too unpredictable to use on moving bodies. For WeldConstraints to be reliable when in use with moving bodies, the server would need to replicate its offset to clients.
If Roblox is able to address this issue, it would improve my game development experience because I would be able to use a more up-to-date joint than Welds/Motors for moving bodies.
More resources:
Dev Help thread: https://devforum.roblox.com/t/weldconstraint-weld-to-player-offset/95574/
Repro: