You haven't, you mentioned it in your first posting.
For the problem, I couldn't make any progress. As I see it, it happens on the evdev level ( /usr/src/sys/dev/evdev ). The keyboard keys don't produce any events. When there is no event no key codes are returned, no keyboard mapping happens. I don't know where to investigate further, also I lack the knowledge to debug the evdev source code.
Those keys of yours returning a wrong function can be remapped, but not the others ( no key codes ). If you need all keys urgent, you could build xorg-server from ports with DEVD enable ( instead of UDEV ), just make sure to pull the right ports tree banch. Package repository quarterly (/etc/pkg/FreeBSD.conf ):
svnlite(1) 2020Q2, package repository latest:
portsnap(8).
If there is no urgency, I suggest you try at
freebsd-x11@freebsd.org mailing list. That list is frequented by developers, familiar with this kind of problem. If you don't get an respons from there after a time you could also try on
https://bugs.freebsd.org. Sorry I couldn't be of help.