It's probably a mag problem. To eliminate the possibility of it being an out of spec bolt catch, put the upper on a different lower you haven't had any problems with, then try all your mags. Narrow down the problem mags, and mark them in some way (piece of tape, marker, whatever.) Put the upper back on the original lower, try the mags all over again, take note if it's the problem mags from the last test, or if it's different mags all together.
If the same mags are causing the problem across two different lowers, the mags are to blame, and couple probably use new springs. If not then, then possibly the follower is out of spec and short enough to cause the bolt catch to miss the follower.
If different mags are displaying problems across two different lowers, it could be that the bolt catch on the RRA lower is out of spec and too short, short enough that it's not reaching the follower.
Worse comes to worst, it's a combination of both out of spec bolt catch and short follower(s). Let us know how it works out.