Hello,
I’m working on an s905x3 Armbian system, and having issues with an intermittent watchdog:
The hardware watchdog: Meson GXBB Watchdog
I’ve got the watchdog service installed.

Expected behaviour, happens 4/5 times: when I kill the watchdog service, it starts wd_keepalive, which keeps on pinging the watchdog. Kill wd_keepalive and after a few seconds the device power cycles, as is expected.
But sometimes that doesn’t happen, and the device just continues running. The watchdog device is also then writable (which it usually isn’t, due to being kept busy by the above processes)

I’ve found this because sometimes the device doesn’t power cycle after reboot: it kills all services(as expected), then remains on, and doesn’t do the power cycle to start the boot.
I’ve also purposefully crashed the kernel a few times, and it displays the same intermittent behaviour: sometimes power cycling and sometimes not.

There’s also a kernel process called watchdogd. The status of that service remains the same under both circumstances, so unsure if that has any impact at all. I cannot kill that service either, but presume it gets killed in the reboot scenario.

Any ideas?

What build do you have installed (full name of the file and location you downloaded from)?  While I used to see this problem with older kernels, I haven't seen this recently with newer kernels.