OPNSense (FreeBSD 13.1-p6) kernel panic

After a recent OPNSense update my HD activity light was staying on and the
CPU meter on the OPNSense dashboard was reading 100%.  After looking for
anything obvious and turning off all the services I could, the CPU was
still pegged and the HD light was still on constantly.  So I rebooted the
machine; it never came back online.

After I attached a monitor to the machine I saw that it had a kernel
panic.  While unusual I didn't think too much of it however rebooting the
machine didn't resolve the issue.  So, I removed all the cards, memory,
etc. to see if I could get a clean boot.  Nothing helped and I continued to
get a kernel panic.

I thought it might be a corrupted hard drive or something so I disconnected
the drive and booted off a USB thumb drive with a fresh copy of OPNSense
v23.1 installed on it.  The system booted just fine and ran the live
version.  So I turned the machine off, reconnected the drive, rebooted and
installed v23.1 on the HD.  The install worked perfectly and the machine
rebooted.  Once again, I got the kernel panic.

My next thought was that maybe the HD was "bad".  I replaced the HD and
again installed a fresh copy of v23.1.  Again, the kernel panic showed up.
Arrggghhh!

I'm running Memtest86 v6.10 right now and it has passed 4 times, so I don't
think it's memory related.  I've replaced the HD so that's (probably) not
the problem.  It seems to work fine when booting from the USB flash drive
(it's just slooooow) so the CPU seems to be OK.

After the kernel panic the machine is locked up completely.  Nothing
works.  The keyboard doesn't do anything, the capslock key doesn't, light
up and the floppy drive light is stuck on.

I've not been able to get a text output of the panic but here is a
screenshot I took from my phone: https://imgur.com/a/aaXwkVK  I posted
about this first on the OPNSense forum (
https://forum.opnsense.org/index.php?topic=32728.msg158386#msg158386) but
they said that this mailing list was probably the better option.

Equipment:
* Acer Aspire AST180-UA380B
* AMD Athlon 3800+
* 3GB RAM
* 1TB SATA drive

Thanx
Richard