Nginx Proxy Manager: Custom locations don't work

[Iacov]

hey

currently i have no custom locations defined in my nginx proxy manager - and per se everything is working fine
yet i'm sure that there is a reason, why there is a tutorial on nginx proxy manager that specifically tell you to add two custom locations
Nginx | Jellyfin

i have added the custom location like in the screenshot below - the proxy host immediately turns from green (online) to red (offline)
no matter if i add "/" or "/socket"

- what am i doing wrong in adding the locations?
- are those custom locations actually needed?
- what are they needed for?

(if it matters, i only use npm for "nice" fqdn's within my lan, no wan exposure)