Still having more failures with these, and not getting very far with the investigations.
Our client still hasn’t seen any failures with the 4.19 kernel (but until now most hardware running 4.19 kernel is an older production batch, albeit with the same eMMC firmware etc. so this might be relevant too).
I’ve noted that the MK2704 ( Kingston EMMC04G-MK27 ) are reporting fast wear rates in comparison to the previous M6704 ( Kingston EMMC04G-M627 ), e.g. 0x03 (which is I believe 30% - 40%) wear after only a week or two of light use (in comparison the M6704s all report 0x0 (which is I believe 0% - 10%).
In case it’s useful for anyone, I’m using this one-liner to gather info:
( echo "BBB hostname $HOSTNAME" ; echo -n 'BBB version ' ; hexdump -e '8/1 "%c"' /sys/bus/i2c/devices/0-0050/eeprom -s 12 -n 4 ; echo ; echo -n 'BBB serial ' ; hexdump -e '8/1 "%c"' /sys/bus/i2c/devices/0-0050/eeprom -s 16 -n 12 ; echo ; for i in name date rev hwrev fwrev oemid manfid life_time serial ; do echo -n "eMMC $i " ; cat /sys/block/mmcblk1/device/$i ; done ) | column -t