Backup Docker Volumes/Duplicati running as root

Hi, Duplicati works like a charm on my daily driver linux host. I’ve decided to use it on my virtual docker host in the cloud,too.
But Duplicati (running on the docker host) fails to backup several named docker volumes. I guess this is a permission problem.
For example; the www-data user uid in my nextcloud-container is 999. Unfortunatly on the docker host this uid belongs to the systemd-coredump user. Nobody except root can read this directories and files
Is there any way to run duplicati service as root? Or an other solution?

Thanks

Moped

What docker image are you using? Official duplicati one, or linuxserver, or…?