Yes, they are prone to having issues, and replacement backcaps are like the #1 necessary upgrade that's actually an upgrade.
#2 would be a Dye Feedneck collar to replace the plasitc one that came with the marker from the factory
#3 would be trigger, CP and others make great triggers that make it more snappy and feel better in your hand
#3 upgrade to an ultralite frame, it's hourglass shape feels better in the hand and it's all metal, but don't be fooled by the name, It's heavier then the stock frame (should be called a heavyweight frame
All or at least most sites have backcaps, some on clearance and you should have no problem finding them. my favorite one is the hybrid traitor cap, second is the modified backcap, but NDZ is the cheapest but still better then stock. Good luck with your pmr, it will last you for years.