System seems to crash at random times, during casual desktop use.
During the last crash the system was very low on Free memory (around
100M according to `top`), while swap was not being used.
I'm not sure if the backtrace  contains the desired output (seems
to start at /usr/src/sys/kern/kern_shutdown.c). When running kgdb in
/var/crash the output points to ULE instead .
The links no longer lead to relevant information.
If you still have the data, you may want to attach it to the report directly.
It would also be useful to know if you can still reproduce the issue
with a more recent FreeBSD version.