Hello again,
I have added an option to set the proxy URL which will directly affect how songs are loaded from your Jellyfin server, you can find this under the new "Proxy" header:

There is also an option which changes the streaming endpoint which may help resolve this issue

I would like you to test this whenever convenient if possible please. I'm happy to send over an updated build to you via Email or Discord (@alexcjw), alternatively this addition will be available in the upcoming version 2.1 which will be released very soon
Thanks!
Alex