Never had any of those, but i did install over 60 of Mesa boards, never had a single issue, ever.
Most of them are in industrial machines retrofitted to Mesa and LinuxCNC, i use 7i92 on plasma machines i build with no BOB's, fully aware of the sensitive I/O and never had a single I/O fail.
So i would venture a guess that something is wrong with the wiring and buying more will end up with more dead cards.