I remember a story of an Oracle Database customer who had production broken for days until an Oracle support escalation led to identifying the problem as mere "No disk space left".
i had to ssh to our public nextcloud and run the occ empty-all-trashes-immediately --force --all-users -f command, due to its disk filling up (2.5TB!) and postgres crashing, to boot. empty-trashes command and a reboot and it came right back up.
It's always lupu... I mean NTP or disk space.