CZ-82 Mag release problem

[NoneMoreBlack]

Just got my CZ-82 from AIM, and one of the 2 magazines it shipped with does not drop free easily if the slide is forward. With the slide locked back, it drops free positively. The other mag works perfectly. There does appear to be a small scratch on the side of the bad mag that lines up with the right-hand grip screw but even taking the screw halfway out does not allow it to drop free consistently. I tried smoothing down that spot on the mag with some steel wool and a bit of lube, still no effect.

Any ideas?

Thanks in advance.

[NoneMoreBlack]

As an update, I did the magazine release repair according to these instructions, with no improvement: http://czechpistols82792.yuku.com/topic/7455/t/CZ-82-Magazine-Release-Stopped-Working.html