I've run both new and multiple-fired RP pistol brass in 45acp, 9mm, 38 sp and 357 magnum through my Dillon Square Deal B without problem over the past eight years. I've also upgraded to a Dillon 650 and still have no problems with RP or other brass. I've got 85,000 rounds through the SDB and about 2000 through the 650, but of course not all of those are RP cases. I've used a mixture of bullets- JHP's from Remington, Speer and Taurus and FMJ's from Zero Bullets and lead casted bullets from AccurateMold molds. Maybe it's related to your resizing dies as others have mentioned. Hope it all works out well for you.
best wishes- oldandslow