Jellyfin hangs even with downloaded movied

[JonathanPi]

Hi,
I have Jellyfin on a Raspberry Pi 4, movies on a SSD via a powered hub.
At home, watching in Kodi on my local network works great.
But outside my network, on my phone (intended to Chromecast), movies hang. When starting, when fast forwarding even stops the movie almost. Even after downloading the movie, this behaviour continued.
Is there a setting that can fix this?

[TheDreadPirate]

How are you making Jellyfin remotely accessible? Can you share your jellyfin logs via privatebin.net?

[JonathanPi]

Hi @TheDreadPirate,

I have Jellyfin on a Raspberry Pi, secure connection by using Caddy and static IP by using No-ip. But does this matter if the movie is downloaded? If I watch on my phone, other times, without downloading, it was supersmooth, no lagging.
It felt like it still tried to stream from the server instead of using the downloaded movie.
Anyhow, I now tried again, and it was again very difficult: it takes a long time before my phone connects to Chromecast and hangs when you pause or skip back or forth.

I switched to my laptop and casting from Chrome (on Fedora) and that went perfect, even without downloading. So it's the Jellyfin-app or my phone that's the problem!

What's the experience of other people? Is casting with Jellyfin on Android working fine for you?