Gamo Swarm magazine problem

[Poteen]

I have a great shooting Gamo Swarm Maximum Gen 3.  I have problems with the pellets dropping through the cylinders when I am loading the magazines.  Gamo sent me 3 new magazines and they have the  same problem  after only a couple of loads.  I am using a variety of pellets and they all drop through the cylinder.
 
   It looks to me like the rubber band around the center of the magazine loses it's tension.  I two cases they broke.

     It's a great rifle but I didn't buy it to have a single shot rifle.

Has anyone encountered this problem and come up with solution

   I am now the proud possessor of 5 inoperative magazines and would appreciate any advise.

Poteen