Often you have to enlarge the hole in the center of the base plate just a little, this allows the retaining plate detent to seat fully in the base plate. If you have a wide selection of drill bits find the drill but that just fits the holes and go up one size to ream the holes out a little larger. Also take note or better yet a measurement of the depth of the distance from the bottom of the base plate to the top of the detent on the magazine prior to reaming out the hole, then re-measure after reaming. This will tell you if it was large enough to make a difference, a few thousands is all that is needed.
Jim
Miossi Gun Works LLC
702 Park Dr
Monticello, IA 52310