Trimag problems--or is it the action?

I've been using a Trimag set-up for a couple of months, and I've consistently had failure-to-feed problems with it.

I wasn't sure if the problem was the weight of the Trimag, or one or more of the individual mags, so I took the Trimag off and shot the mags separately--no FTFs!

So, what I'm wondering is: is this a common problem with the Trimag, or is the mag retainer in my action gunnybagged? The action is a '92, and has seen hundreds of bricks of ammo, so wear is a consideration.