You know, this is something that has irked me for close to 30 years. The guy I bought my first 742 from was a smith, and when I had a problem with the magazine a couple of years later, he said I should buy a new one.
This past year, when I went online and corresponded with some gunsmiths on this same issue with my new 7600, I got pretty much the same response.
Here's what I've gleaned from 30 years of dealing with the problem:
1) A lot of people say this is a blue elephant in the corner for Remington. They just don't want to think about it. It's a gnawing design flaw, but they can't change the design without admitting there is a problem. The main flaws as I see them are there isn't enough area front and back on the lips, and the metal of the magazine is not stiff enough to maintain proper length front-to-back.
2) There isn't a whole lot of 3rd party magazines that do any better. I've tried some. The problem is the whole attachment design, not the magazine itself.
3) Gunsmiths don't want to wade into it, because the problem will usually re-occur, and then the gunsmith is stuck with the problem like a tar-baby. They would rather have you go out and buy a new magazine.
4) Part of this is being absolutely fastidious in how you insert the magazine. If you don't do it just right, the magazine gets munged up. Some of this is beginner's learning curve. However, I'm a 30-year veteran of these magazines, and I still managed to bend up 3 of 4 magazines over a 5 year period.
Bottom line: This is not the kind of magazine attachment you find on a AK47 or an M16. The mags themselves are prone to slight disforming. It is a largely insoluable mess. All that being said, I still don't regret my 742 or my 7600.