I had a similar problem with a Scorpion-10 mag when the multi-shot Scorpion first came out (same mag system). BSA did replace my broken mag, but there again, my gun was only three weeks old at that time (since sold said Scorpion-10 as now prefer sing-shot rifles for real-time air-gun hunting).
I spoke to the BSA guru John Bowkett about this mag problem around that time, too, and he advised strongly, that once a shot is taken, to pull he trigger back and release it once more before drawing the bolt to rotate the mag and load the next pellet. This I then did from that point on, and never had any such magazine problems, again.
Good luck contacting BSA about a new mag, and I hope the above pearl of wisdom courtesy of Messrs Bowkett, helps?