create a variable called TargetRotation and set that as RepNotify
dont use SwitchHasAuthority, use IsLocallyControlled
On Tick update your TargetRotation and set it on ServerOnly with an RPC,
On Repnotify SetActorRotation with TargetRotation
Or it may be SetControlRotation, im not in engine right now
No Multicast Required.
Also make sure nothing else messes with the Rotation, ie OrientRotationToMovement