My 3.1 moodle instance on AWS has started to act wonky (actually quitting altogether for a while)
Won't backup or restore,
Won't display site logs (but will display other logs)
It appears to have trouble writing temporary files.
I have tried to accelerate some of the cleanup routines, and the site has started to speed up (its night-time now)
It seems to keep all of the logs (from a year ago to now, every mouse click)