I'm surprised that nobody has replied to you yet.
I can think to two possible quick fixes based on my experience with rimfires and my PT99. However, I don't have any experience with the Ceiner conversion (although I'd like to get one).
First, be sure the conversion unit is very clean and well-oiled, especially near the firing pin.
Second, try different kinds of .22 ammo. Some of the less expensive stuff may (possibly) have less primer in the rim.
Otherwise, it sounds like you may have some sort of a trigger problem. The only reason I mention this is that you shouldn't have to decock it the pistol doesn't go bang after a single action trigger pull. You should be able to simply pull though in double-action.
Good luck and keep us posted.