I own 3 Scherer mags 29 rnd in 40, and 3 Glock mags 33 rnd in 9mm.

So far the Scherer mags have been perfect with no problems at all.

One of the factory Glocks I got new , I had to take apart and deburr two corners where the metal liners meet in the middle, the follower would stick.

Like anything, just the luck of the draw I imagine!