File the inside edge of the handles along the edge for the entire length so there is no chance of the handle touching the mold Do this carefully, but the inside edge needs to only be strong enough to pull the mold apart.
RCBS handles are not necessarily square to the screw holes. My early RCBS handles show edges suggesting they were sheared rather than profile machined. This causes the mold to be pressed in some point that the mold faces are not able to close completely. Lee handles are thin which allows the mold to align as it pleases until full closure. Today, the RCBS handles have better profiles.
Country boy from Western Illinois, living in the Magical Pacific Northwest