Hello again!
Our new parts came in last night (yay Amazon!) and we decided to to take a strategic approach to troubleshooting. Our tech swapped out the cheapest part this evening (it only took 10 minutes so there was no time for a warning post) and we'll just see if that cures our shutdown problem. Fingers crossed!
Thank for your patience, Winners!
Edit: Having the server offline created a time synch issue that made it impossible to post for a few hours this evening. All has been fixed. Apologies...