Re: Glock trigger upgrade gone wrong
Based on the OP's description, this is clearly not a shooter related issue.
I have had the same thing happen with a G19, although it was not with a Ghost connector, it was after a "$0.25" trigger job that was just using some Flitz to polish the engagement surfaces of the stock trigger bar, connector, firing pin tail, and firing pin safety. When I did a dry fire function check the pistol would consistently "fire" (firing pin released) during trigger reset. I didn't bother live firing it as I knew it was a no go. Ultimately replacing the firing pin safety (thankfully the cheapest part of the four) fixed the problem.
My situation was a bit different from yours but here are my recomendations:
1. Stick with factory Glock parts. The competition style triggers/connectors/firing pins can be tempting, but they usually result in trouble. The Glock (-) connector is a great connector, and that is all I will use or recomend. The only non-factory parts I use are a Vickers Tactical slide release lever, and 10-8 sights. Aside from those and a grip texture job everything is stock. I will do some light polishing of parts, but I always check function afterwards.
2. Do your own work on your Glocks. It is easy enough to learn, the tools are cheap, and it gets you more aquanted with the inner workings of your pistol. You will also know exactly what has been done to yout pistol. Maybe your gunsmith did some additional polishing to your trigger parts and that is what is causing your doubling issue?
For now go back to stock parts, and check your firing pin safety to see if it has been modified. Going back to stock should fix the issue for now. If you want a lighter connector, go with the Glock (-) connector.