I'd have to install it again to remind myself of all the specifics, and as I'm happy with Emby I probably won't dedicate any further time to it. What I deduced was a Linux environment for Jellyfin was better all round.
It didn't support mapped network drives or shared drives on a Windows Server correctly.
I tried using public shared drives with no security and all manor of other credential scenarios and it just didnt like the environment.
As soon as I installed Emby within minutes I'd configured the server within the environment I wanted to use it with so I knew there was something not right with Jellyfin & Windows. I recall there being many posts about it with many suggestions and no solution.
This post is close to the problems I was having, based on this thread, the guy doesn't confirm anything he tried worked.
https://www.reddit.com/r/jellyfin/co..._mapped_drive/