Cron not doing its job (Docker)

As described in the title, my cron just does not want to run correctly…

To not create the wrong impression, it seems to kinda run… at least that’s what docker-compose up tells me:

nextcloud-app      | 192.168.2.221 - Knallbert [28/Sep/2020:20:11:50 +0200] "PUT /remote.php/dav/uploads/Knallbert/2348113677/00000000 HTTP/1.1" 201 785 "-" "Mozilla/5.0 (Windows) mirall/3.0.2stable-Win64 (build 20200924) (Nextcloud)"
nextcloud-cron     | crond: wakeup dt=60
nextcloud-cron     | crond: file www-data:
nextcloud-cron     | crond:  line php -f /var/www/html/cron.php
nextcloud-app      | 192.168.2.221 - Knallbert [28/Sep/2020:20:11:58 +0200] "MOVE /remote.php/dav/uploads/Knallbert/2348113677/.file HTTP/1.1" 201 927 "-" "Mozilla/5.0 (Windows) mirall/3.0.2stable-Win64 (build 20200924) (Nextcloud)"
nextcloud-app      | 192.168.2.221 - Knallbert [28/Sep/2020:20:11:54 +0200] "PUT /remote.php/dav/uploads/Knallbert/3597273656/00000001 HTTP/1.1" 201 785 "-" "Mozilla/5.0 (Windows) mirall/3.0.2stable-Win64 (build 20200924) (Nextcloud)" 

but nevertheless it seems to not satisfy nextcloud (switched from AJAX for this example… obviously I normally still need some kind of cron-esk trigger for routine things):

Unbenannt

I am running a docker container with docker-compose.
My docker-compose.yaml more or less is this docker-compose.yaml .
In there the cron container is defined as followed:

nextcloud-cron:
image: nextcloud
container_name: nextcloud-cron
restart: always
volumes:
- /home/nextcloud/storage/app:/var/www/html
entrypoint: /cron.sh
depends_on:
- nextcloud-db
- nextcloud-redis

I did all the googling and the duckduckgoing but could, for the life of me, not figure out, what’s wrong with my configuration…

Please help!