There is a small hole on the side of the RT Valve that is leaking. After watching the videos and ordering new rings, I replaced the prescribed Reg. Seat O-ring.

This did not repair the leak.

Is there a second point of failure for this leak?
Is this hole a pressure relief point?
Is it possible to install the Reg. Seat O-ring incorrectly (seems rather difficult to mess up)?

Thoughts would be appreciated.