Did you put in the locking block pin first? If you put it in after installing the slide stop then you probably damaged the slide stop spring and that may be what is causing the malfunction. I don't think it has anything to do with the trigger mods/parts.
When you reassemble a three pin Glock, the first pin that goes back into the gun is the locking block pin. That will help insure that the slide stop spring doesn't get damaged during reassembly.
When you reassemble a three pin Glock, the first pin that goes back into the gun is the locking block pin. That will help insure that the slide stop spring doesn't get damaged during reassembly.