The 'Synchronize Position' flag on an UdonBehaviour doesn't work

Hi all,
I’ve searched around for this specific problem, but I haven’t seen anyone experience this before.
I have a few objects with an UdonBehaviour, a VRCPickup, a Rigidbody, and a Collider. The ‘Synchronize Position’ checkbox is checked. However, when I build the project and move the objects around, other clients (running on different devices) don’t see those movements. Anyone know why this may be?