Did the first gen mags have the metal sleeve inside? I know a buddy of mine that was in the FBI said if they ever had a jam the first thing they did was throw away the mag. For the most part the Glocks functioned extremely well. Most of my pistols have never had a malfunction. I have had one with my Glock 27, and one with my duty HK. The Glock was a mag issue. The P2000 jam was due to shooting this weird “green” ammo which got the guns very dirty, then going to lunch and coming back and shooting more. The grime left behind by the green ammo was almost like sludge. I just wiped my thumb across the feed ramp and it started behaving. Never had any problems with normal duty ammo.
I honestly don’t remember, and the RO gave me the same advice you just did, get rid of it, and I did. I don’t have enough spares for that piece is the real issue. Now I have a Sig to feed (that also takes .40 Smith and lo and behold! Santa left me a .357 Sig barrel and a couple of mags as well). It’s kind of a nice problem to have, but I still need a few Glock mags.