[Hectic]

The trigger issue im not sure about as ive never had that. Is everything lubed well?
The not locking back. I find if i fire full auto itll not lock back on occasion.
I belive its due to cooldown causing the bolt to not cycle fully. Will tue bolt lock back if you manually charge it with an empty mag in?
Could be a worn mag catch or the part on the mag is worn.

Also i think you should lock the bolt back befor inserting the mag just to save stress on the nozzle feed ramp thing.

Hope you figure it out. How ya like it other then the lil issues your having?