Looks like you did well with your new to you Gen 3. A couple months ago I bought a Gen 2 G22 trade in and no problems with it at all. Don't know which PD it's from but it has the standard trigger. Nothing wrong with the NY1 trigger, some people like the heavier pull but you can change it out easily if you don't like it.
How many magazines do you have or have access to? Some old Glock mags and Korean mags won't drop free so you might want to try a new Glock mag to be sure your problem isn't the mags instead of the mag release, which rarely gives problems.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek