If you put that request in the repeater (in Burp), you can test with and without the double slash. See if you get a different response.

I personally doubt that the double slash is an issue. Maybe there's information in the response or its headers ?
Do you guys test with the preview branch of Sonarr? I can't get nzb360 to connect to my instance of Sonarr through Burp proxy anymore. I'm currently running Sonarr version by linuxserver.io. I don't have issues with other nzb apps like LunaSea. They all display episodes properly. Only this one has an issue.
For some reason this issue is back. The page for any TV show shows no episodes.

I've got the following cipher suites enabled on traefik, my reverse proxy:
- "TLS_AES_256_GCM_SHA384"
- "TLS_CHACHA20_POLY1305_SHA256"