Check the regulator valve pin oring. If that oring leaks, it can feed through the regulator pin assembly and keep a flow of air going to the chamber even if the on-off is closed.
The RT had a whole assortment of on-off pin length configurations available. The 0.760" pin length should work fine.
The trigger should be about a credit card thickness in front of the trigger rod when the trigger is held against the safety with the valve aired up and ready to fire. If the trigger is making contact with the trigger rod, it is too long and will cause short stroking and recharge issues.
Except for the Automag in front, its usually the man behind the equipment that counts.