My CQB doesnt lock back with certain mags on random occasions. I went through and marked the ones it didnt lock with(about 8 of my 22 mags). Today at the range, a few that weren't marked failed to lock back too. What causes this and how do i fix it? Every mag locked back fine with both my LB UTC and STI Trojan.....just not with the CQB. I did have a short trigger installed in the CQB by a local smith since getting the gun......not sure if this can cause it? The gun ran fine otherwise. How do i fix it?