Massive bandwidth saturation when adding library

[Martin]

I have just installed Jellyfin for the first time, and when adding a new folder to the 'Movies' library (it's on an external disk), the machine I was using remotely from another part of the apartment, over RDP on Windows, became inaccessible due to massive saturation of the network bandwidth.

I had to force-kill the server to stop the bandwidth-hogging, and have not allowed Jellyfin to run since then, until I can get more information.

Is JF possibly doing delayed downloading of components? This was an uncontrollable bandwidth black hole, one of the worst I ever saw, and I would be glad to know if anyone can guess if Jellyfin is really the culprit here.