So after a few months of smooth sailing with XenForo, this few days I've seen the forum went down a few times with the error message "An unexpected database error occurred. Please try again later." I would reboot the server and it would go back up, only to have the same problem reoccurring after a few hours. Also during this period when the forum is online, sometimes trying to open certain threads return the same "An unexpected database error occurred. Please try again later." Any clue what to look for?