weird boot problem on rpi3

[tech-lists]

Hi,

I'm running a headless rpi3 with freebsd-12 r343022. It's self-hosting -
by that I mean I've built/installed world/kernel on the device more than
once. It has a wifi dongle, a usb-powered hd and a wireless keyboard dongle
plugged into the usb ports. It all works great, apart from the following
problem:

If the rpi3 needs to reboot, it will not come back up again unless the
keyboard dongle is plugged in (and the keyboard itself is turned on). It
doesn't matter if the other peripherals are plugged in or not. To come
back up again, the keyboard must be turned on and its dongle plugged in.
It doesn't matter if I use shutdown -r now, poweroff (then unplug/plugin
power) or halt then powercycle.

I have plugged in a monitor to see where it fails. It fails at the point
where a probe to the keyboard would be expected. It just sits there and
doesn't proceed. There's no error 'no keyboard detected' or anything
like that.

How can I fix this?

thanks,
-- 
J.