More than likely the front of the trigger sear is hitting the slot it protrudes through in the receiver. When the sear is engaged by the CP, it pushes forward slightly, see if it is contacting the receiver. It's all spelled out in the instructions. If there is interference, relieve the slot accordingly. Or, send it to a professional.
I'll have to check it again once I get back off work. I tried calling Timney again, still unable to reach anyone on the phone.
