the RMS I bought at Autozone is a FelPro...which is a very good seal. They make 2 types, one rubber and the other Teflon. Get the rubber one. If you installed the Teflon one with oil/grease it can leak. Teflon seals need to be installed dry
RMS leaks are not common. typically the rear intake gasket or oil sending unit leak and migrate down making it look like a RMS leak. Also the oil filter adapter can leak .
If you are tearing this apart again (big fing job) than really confirm wtf the leak is coming from. I used a oil dye kit to find my leak that I thought was RMS. It was the RMS adapter plate seal that was leaking which requires the pan be dropped also to remove it.
Confirm there is no wear groove on the crank where the seal rides on.