I’ve never seen or had any problems with 50 rounds mags.
I personally think Koevoet used the 50 rounds mags more than any other South Africa police or military unit in action. The success of the 50 round mags speaks for itself if you take in mind that this unit fought in more than a 1600 contacts. For example if the 50 round mags were only used in 10% of these contacts it were proven 160 times, that is already a positive result IMO.

Sand blast and blue your old mags.