I have 3 5-round and 6 10-round MK1919 style 12 gauge magazines. I'd loaded them all up for a range trip that didn't happen because of catastrophic failure of my rotator cuff back in Aug 2023, It has been a long recovery from shoulder replacement surgery, but I finally got to the range again last Wednesday and all magazines fed and fired without issue after sitting loaded in my range bag for like seven months.
If the mags are loaded correctly the rims sit on the metal part of the shell with none of the plastic bodies touching anything above or below. I don't know if the other similar but not compatible magazines do the same, but it doesn't appear to be an issue with the MK1919 style mags.