Hello Geoff Tree, I am not involved in packaging mousepad, but tried to reproduce the issue. Unfortunately I could not trigger the crash.
Maybe you could install a coredump collector like systemd-coredump.
The last lines of the output of the command 'journalctl --no-pager'
should give the location where the next crash happened.
Some other hints about collecting more information
are in the following document:
https://wiki.debian.org/HowToGetABacktrace
Kind regards,
Bernhard
