The vanilla install of Sonarr leaves out the ‘/’ symbol in <UrlBase>, causing 503 errors if not corrected.
Steps to reproduce :
Vanilla install QB
Vanilla install Sonarr from QB Dashboard
SSH into box
Examine ~/.config/NzbDrone/config.xml
<UrlBase>sonarr</UrlBase> should be <UrlBase>/sonarr</UrlBase>
I think this is pertaining to your installation alone. Not sure what is happening there without having any specific reports, however, it should remain <UrlBase>sonarr</UrlBase> as expressed in the config.xml template. I just ran a test on a server and there is not an issue. Can’t say this is a bug as many others have ran the Sonarr installation as is without issue.