A "bolt over base" or "hit the shell in the middle" is not an unknown thing, it is the result of the magazine spring not getting the round "back up" at the proper time. Recoil (and inertia) drive the rounds down in the magazine, and if the spring (for whatever reason) doesn't push them back up, fast enough you get bolt override.
The internet, and engineers, will tell you that springs don't wear out from being compressed, they wear from the cycles of compression and relaxation, and that properly made springs won't "take a set".
However, the only way to know if your spring wasn't properly made is when it does take a set or get weaker.
If you switched ammo, and the new stuff has more recoil than the system is set up to handle, you could get bolt override. If the mag spring has weakened, same result. If there's crud in the mag retarding movement of the follower, same result. If oil has turned to sludge, same result.
Did it happen with ALL your mags?
Order some new springs. If they cure the problem, fine. IF not, they're still good to have around, someday you'll want them.
Make sure everything is clean like it should be, and test things with different ammo.
Good luck!