I also run this on Synology and struggled with folder permissions. It didn't matter if I ran it through the synology docker GUI or command line with enhanced privileges/admin, could not get the container happy with the permissions so was running without persisting the data folder. But I finally stumbled into a solution. If you manually create permissions to read/write for the target folder in File Station, everything works as expected.
There may be a more elegant way to get it working in Syno-Docker, but this worked.
Thank you @m0ngr31 and Channels. While a bit finicky at times, this is truly a game changer for sports fans. I love having everything in one place with a simple, consistent interface. The ESPN+ interface is atrocious.