Need help with Diagnosis Internal server error 2 weeks after 20.02 update

Hello all
I need help with some preliminary Diagnoses. My Nextcloud install has run without any issue starting with version 18.04 through now at 20.02 for 8 months on Ubuntu 20.04.
I ran periodical Nextcloud backups and ubuntu backup.
The first time I saw this error I was shocked and thought it was a hardware issue because it gave no warning, I found out my OS drive which Nextcloud is installed was mysteriously full for no reason, I had a previous install which Nextcloud which did crash the server from a bloated log file. I performed an auto-remove which cleaned out about 145 Gb and then rebooted. Nextcloud still had the 500 internal server error until the next day and then started running fine again. I watched all the system resources with several browser pages open and test videos playing never made a dent in performance.

Nextcloud has crashed this time after 4 days of constant use. I found Apache2 had an error after running: sudo systemctl status apache2 I tried restarting Apache no luck.
I had to reload: /etc/init.d/apache2 reload got me the green active.
MariaDB status Active.
I have a lack of knowledge and need help with how to retrieve the Nexcloud log. also if possible how to retrieve and run my backups from the command line.
Thank you.

Continuing the discussion from 500 Internal Server Error, The server encountered an internal:

The only solution was to repair Apache2, Mariadb, and Redis. All data was saved.