I only load 3 into my 7600 mag. The spring tension tends to struggle when 4 rounds are used. If the mag has extended use then the spring may be shot. Take some bore scrubber and clean out the mag as there may be dirt in there.
Take a plier and bend the lip outward on the short front side. Bend very little. It may help stabelize the mag. I nothing works then buy a new mag. This mag will run you $29 -32.