Bought a mkII off another user here (said he had no problems with the pistol but it's having quite a major issue). Took it out without cleaning and the bolt doesn't always return to battery to reset the trigger. It feels like it may be getting caught on the trigger (?) because sometimes when I pull the trigger, the bolt will finish the travel forward. This is with or without ammo. Does it still after a good cleaning and lube job, any ideas?