Being an incorrigible brass hound, I've probably had more than my fair share of "ringers" over the years.
IIRC, all of them have happened with range pick ups that have sat out in the weather for a while.
Usually they happen in one's and two's, so they just get tossed into the recycle bucket.
A few years ago I ran into the mother lode of .30 Carbine brass, over a thousand 1952 & '53 WRA cases laying in piles at one of the local LE ranges (I don't know about the rest of you, but finding ANY reloadable .30 Carbine brass is rare for me).
Unfortunately about 2/3's of them gave that little "tink" during depriming that tells you a primer has separated.
I tried basting them in Kroil for a week before decapping and it may have helped a little, but I continued to have a lot of primer bases pop off. I decided to come up with a way to salvage those cases. (My apologies, but I didn't take pics when I was originally working out the process, these photos were taken later with a random .45 ACP case).
I decap and reload Berdan brass and use the "punch and pry" method on stubborn cases, so I already had an old Allen wrench modified into a chisel with a concave point ground on it.
I removed the decapping stem,, then screwed the resizing die into the press from underneath and used the lock ring to hold it in place. Then I used a small hammer to drive the chisel into the primer wall (don't go too deep or you'll trash the primer pocket).
Once the tip of your chisel has a good "bite", start tapping on the other end of your chisel and the stuck primer "wall" will pop right out.
At this point you've got a fully deprimed case, but it's lightly stuck in the resizing die. My solution was to grind a flat surface onto the end of a 4 inch deck screw, then place the head in the shell holder with the flat end positioned so that when you lower the press handle, the screw will push the case out of the die.
Getting everything set up takes some time, but once you're ready to go it only takes a few seconds per case to salvage what would otherwise be scrap metal.
Aside from time, a 4 inch deck screw and a worn out Allen wrench, there's no cost involved in this process.
It's probably not worth the effort unless you have a fair number of ringed cases, but it's easy and cheap to fix 'em if you don't mind spending a little time.