Trap 12

I've just fixed an old ThinkPad X21 which was lying around for some time. It's quite underpowered by today's standards but meets the minimum hardware specs for FreeBSD so I thought I'd try running FreeBSD on it. I inserted a disk which had an existing FreeBSD installation on it
(10.2-RELEASE-p9). It seemed to boot up OK but then stopped with a Trap 12 before the login prompt.

Anyone know what is happening?

Incidentally this does not happen in single user mode.
Most of the time they're caused by hardware issues. As this is an old machine I'd make sure the hardware itself is still good, especially memory.