Internal Server Error - Supposedly space issue

Hi helpers,

I am using:
Nextcloudpi v1.25.0
Nextcloud 18.0.4.2

Since yesterday I get following error message when trying to reach NC via browser:

Internal Server Error

The server encountered an internal error and was unable to complete your request.
Please contact the server administrator if this error reappears multiple times, please include  
the technical details below in your report.
More details can be found in the server log.

I was heavily updating music stored on NC over the last days. Several GB. Only editing tags, so no increase of space. But I got a warning in NC Windows Synch Client, that I ran out of space.

Checking disk space of my Raspi: Max. Load of SD card, and attached USBs is 71 %. So no issue.
I even can not restore backups from Nextcloudpi. While trying, the page is loading infinately without properly displaying anything.

Apache seems to be up and running. At least checked via ‘sudo service apache2 status’ via SSH.
Rebooting Raspi needs over 5 minutes to be able to connect via SSH.

This is an error log from /var/log/apache2/nc-error.log

[Sat Jun 06 11:36:25.372120 2020] [access_compat:error] [pid 9384:tid 1465861152] [client 192.168.0.10:61750] AH01797: client denied by server configuration: /var/www/nextcloud/config
[Sat Jun 06 11:38:12.287333 2020] [proxy_fcgi:error] [pid 9383:tid 1646253088] [client 192.168.0.10:61803] AH01071: Got error 'PHP message: PHP Fatal error: Uncaught RedisException: MISCO$[Sat Jun 06 11:38:12.322547 2020] [proxy_fcgi:error] [pid 9383:tid 1560249376] [client 192.168.0.10:61774] AH01071: Got error 'PHP message: PHP Fatal error: Uncaught RedisException: MISCO$[Sat Jun 06 11:38:12.524004 2020] [proxy_fcgi:error] [pid 9384:tid 1491039264] [client 192.168.0.10:61809] AH01071: Got error 'PHP message: PHP Fatal error: Uncaught RedisException: MISCO$[Sat Jun 06 11:38:53.700297 2020] [log_config:warn] [pid 9384:tid 1482646560] (28)No space left on device: [client 192.168.0.10:62046] AH00646: Error writing to /var/log/apache2/nc-access.$[Sat Jun 06 11:38:53.903876 2020] [log_config:warn] [pid 9383:tid 1654645792] (28)No space left on device: [client 192.168.0.10:62049] AH00646: Error writing to /var/log/apache2/nc-access.$[Sat Jun 06 11:38:54.016943 2020] [log_config:warn] [pid 9383:tid 1646253088] (28)No space left on device: [client 192.168.0.1:62040] AH00646: Error writing

Stating a space issue. But there is plenty, as written above.

If you need further information, please do not hesitate to get back to me.
Thank you very much in advance.

Aircan