Quoted from NicoVolta:........Always check the underside of the relay ladder. Oftentimes (especially on score relays) the metal plate is worn away by the coil. If the wear is deep enough, the coil will occasionally catch in the groove and stick to the plate. “Residual magnetism” is often blamed when relays stick, but plate gouging is the more common cause. Use the sanding flapwheel to smooth the underside........
You are right about the wear causing an issue. I have however, moved away from this fix method during restores to a more simple fix?
Remove the ladder and drill out the rivet and flip the plate 180 deg. Add new rivet. Done for another 50 years and then you get your flap wheel out. I batch fix the plates during a restore so a games worth of plates are done in 10 mins. You may also need to add a brass rivet to the contact point with the relay sometimes too on many games so you need rivets and a punch on hand anyway.
I enjoy your write ups, keep going.