Just got a reply from the nextcloud devs. Add ,0.0.0.0/0 to the end of the allowed wopi hosts without removing the ones there. It persists after container restart. Just tested it on my instance.
I'm having the same issue but on Ubuntu server. tried running this command: 'docker exec -u www-data -it nextcloud-aio-nextcloud php occ config:system:set office_wopi_allowlist --value="$ALLOW_LIST"' My config file is updated with the new value but it still goes back to defaults.