MariaDB seems to crash and restart itself, giving a massive dump of error logging. This has happened to us on three separate occasions. I unfortunately don't know much else about what's going on. Please let me know what further information I need to provide.
Since the error logging was too long to post in the description here I have dumped it to a Pastebin link that can be found here:
https://pastebin.com/Yv4fHNF3
, I have also attached it to this ticket.