As a competitor, I would be planning my stages around a division capacity start. So if my mags are not co-operating, chances are my game plan isn't going to go accordingly.
If I was limited to only 3 mags that day and couldn't be without the faulty mag, then I would use it for my reload or as my 3rd.
As an SO, if I saw a competitor having a legit problem with their mags, I'd offer some advise that would enable them to stay within the rules while avoiding any accusations of wrong doing.
It's easy to spot a competitor having legit troubles. In this case, if I were running Trace and he went to slide lock prematurely, it would probably result in Trace trying to still squeeze off a round not realizing he's gone to slide lock. His natural reaction would probably be to drop the mag and reload. The SK would probably see that the recently dropped mag had ammo still in it. If he tried to give him a PE for it, I would be there to argue that the competitor had a malfunction.
I'm one of those weird people that likes to assume the best in others. If it was found that a competitor was doing something to gain an advantage, I'd probably consult with the MD and see if a PE or possibly an FP were in order.