I installed one yesterday, had to be milled .100" to clear the safety. I'd guess your guy removed to much metal allowing the trigger/sear edges to get too close in safe. As little as .005" too much removed can cause issues.
Not enough overtravel adjusted into the system can also cause safety issues. Maybe that set screw/ nut came loose.
This is a great example as to why the cheapest price may not be the best idea.
Edited by TDK (11/01/15 02:36 PM)
A.M. Little Bespoke Gunmakers LLC.