I don’t use Radarr/Sonarr but this seems to work for me with Docker 18.06 and a Media share:
mkdir /shares/Media/downloads
mkdir /shares/Media/movies
docker volume create radarr_cfg
docker create --name=radarr \
--restart=always \
-v radarr_cfg:/config \
-v /shares/Media/downloads:/downloads \
-v /shares/Media/movies:/movies \
-e PGID=0 -e PUID=0 \
-e TZ=America/Los_Angeles \
-p 7878:7878 \
linuxserver/radarr
docker start radarr
Note the trailing slashes in the paths are removed.
Any files in the directory show up in the file browser too.
