Are you hearing an audible click when you pull the trigger?
If so it is possible the screw you added is in too far serving as an overtravel screw as well as the spring retainer. I've made this modification myself.
If the overtravel limits the trigger movement too much, then the sear will "drag" on the trigger itself when pulled. This will slow down and stop the sear before the firing pin is fully released.
Just a thought being you said it went "click".