Archer
··Omega Qualified WatchmakerI've serviced this movement a few times and the rotor is a common problem.
The rotor has a brass bushing that sits on a steel axle (on the automatic bridge of the movement). If not serviced for a long time, the brass bushing will wear out, the rotor will start having up/down play and eventually start rubbing on the edges of the movement (or caseback). It's an easy fix to replace the bushing IF you can get one. Omega doesn't sell the anymore. Even accredited Omega watchmakers apparently need to send in the old/worn axle in order to get a refurbished one.
They need to be reamed to final size using a straight reamer (not a cutting broach, which is tapered) - Omega sells the reamer as well: