Thank you for your answer and time, Jason, it’s really appreciated.
Per your request, I’m also adding firstname.lastname@example.org to the list of recipients.
The failing SD-cards are for the most part the consumer SanDisk Ultra A1 SDHC 16gb, but we also have a few Kingston industrial 8gb (SDCIT/8GB B0623-004.A00LFTS).
They are bought through official distributors of the respective brands, and not likely to be fake, although we have not performed tests anywhere near as detailed as the one you link to.
Talking with the distributer, I’m told that they internally have 0.08 % failure rate on the consumer SanDisk, and less than 0.00 % of the industrial Kingston.
The datasheet for either card makes no promise in this regard, except 5 and 10 year warranty. I’ve asked for further details, if possible.
We have already planned to make the root filesystem read-only (and later move it to the eMMC). The ‘overlayroot’ suggested by Robert Nelson may come in handy here.
However, will this solve the issue?
Afterall, what we experience is not filesystem corruption, which is what we would have expected, but that the entire card becomes unreadable/unrecognized.
It looks to us that the problem can occur to the card at different points in time: