Reboot loop "Kernel Panic - not syncing" after scripts/init-bottom on A20 board / Mainline 4.6.3

Hiya,

Using a Banana Pi M1 as a factory production tester in China, running Armbian Mainline 4.6.3.

Works fine here; never had the problem they're reporting, but they're saying:

a) after a certain amount (unspecified) of time the boards crash and get stuck in a reboot loop displaying screen as shown in JPEG - "kernel panic not syncing - Attemped to kill init! exitcode=0x000000b"

b ) rewriting the SD card image (from one I provided; a 4GB pre-configured image) fixes it (until it happens again)

c) Only useful thing I can get from the photo attached is that the stack trace in the image (which is all I have to go on btw; trying to get a copy of the bad SD card now) indicates CPU0 is in "gic_handle_irq"; assume this is handling an IRQ from the NIC (gigabit on BPi) but it's not clear to me why that would happen (the boards do have an active wired LAN connection, don't know if it's 100 or 1000mbps)

d) Obviously "SD card corruption" is an answer but it's never ever happened on my end and (for example) the fsck is shown passing 

e) The app this thing runs is not writing much to the SD card at all; the image I sent them occupies something like a 1.5G (it's a vanilla mainline Armbian server image with a few tens of megs of extra packages and stuff). I don't know the SD card brand they're using. I use fairly cheapo 4GB SDs on my board (because I like to be able to pull off the image and I don't want it to be huge from say a 32G card); I send them this image (once I'd set it up) in a zip that was just under 1G. I believe they then wrote that onto 8G cards (not sure). I don't know if the image will have expanded it's filesystem to their SD size or if the resizefs only happens on firstboot.

Any suggestions to figure this out and prevent it happening would be very welcome, thank you! If I can get them to upload their broken image to me I'll be able to do more poking at it.

Cheers, much appreciate your time.

DrTune.