I’m not able to get it to replicate movement using Unreal’s replicate movement this way.
If instead you Add a cube, Add a blueprint to the cube, Set the cube to simulate physics, Set the blueprint to “replicates” and “replicates movement”, then Unreal’s Replicate movement will work and so will Smooth Sync (with SetOwnerToServer checked, EDIT: and “replicates movement” unchecked).
If this is not the problem, can you give me some screenshots of your Actor you are trying to sync? Also any other relevant information to recreate this issue will help.