I had this experience as well within the past 2 years, although I was eventually able to get mine apart with a plastic mallet. I think a while back there were some complaints about fitting of the trigger assembly on the RH series (maybe unlatching under recoil?), and Ruger has decided to error on the side of making these units extremely tight (think hammered together) because many users will never have them apart. I eventually pried mine back (the correct direction, opposite the SP/GP/SRH series) using something like a screwdriver blade as a spacer and found that (1) the plunger was bent due to being forced and (2) the latch hole in the trigger assembly really needed deburring/polishing. I called for a new plunger and have been good since replacing it. Even with the polished plunger and hole, I still find that I sometimes need the plastic mallet to disassemble/reassemble the trigger assembly with the tighter fitting. This really isn't an issue for me since I more or less only have it apart to do work on the trigger assembly components.