After some additional research, it turned out the best long-term thing to do was to re-open the GitHub issue for the mate-power-manager project. The previously-fixed bug was an outstanding issue in Centos 7 that they fixed pretty quickly once I did that. Very much appreciated!
I can definitely answer your first question - I'm experiencing the same issue since upgrading to Debian 10 (Buster): a complete freeze every few days.
As for debugging, I'm not so sure. I've posted my own question (System occasionally crashing since dist upgrade) and haven't had any help yet.
My own (limited) debugging methods so far:
sudo less /var/...