Actor attachment offset wrong on clients while pawn is possessed

Hi, I am spawning an Actor as a child of the player’s pawn (on the server). This Actor is attached to a socket on a static mesh for the owning pawn (again on the server side) and both are set to replicate their movement. On the server, the attachment position is fine but on the client, although it does move, its attachment offset to the pawn is wrong.
If I eject the controller for the pawn - the attachment position on the client changes to correct. Possessing the pawn again breaks the offset once more.
Can anyone advise me on what I might be doing wrong?
Thanks.