Currently, freezing an object to world with a VRC Constraint of any kind does not have any syncing capabilities; any object frozen to the world will appear to be in a different position for remote players, especially if the object was in motion at the time it was frozen. Joining an instance late or loading/reloading an avatar late produces similar issues.
I would like VRC constraints to have an option to automatically sync their positional/rotational data to remote clients; ideally this would take place only on an as-needed basis (e.g., when the object is first frozen, or the avatar is first loaded while an object is frozen) to limit the performance/network impact, as well as being an opt-in toggle rather than on by default for all constraints. Current solutions are very clunky and consume a large amount of parameter memory, so I foresee this being a large improvement to systems which require this feature.