Jellyfin for AndroidTV 0.18.8 Playback Issue

[besenwesen]

Hi Everyone,
this post is structured as follows: Background, Problem, Setup, Nice words. If you want me to be precise on something in particular, don't hesitate to tell me :)

Background (skip if not interested):
I moved my Jellyfin Docker instance from an Intel NUC to a Supermicro Server (Xeon Silver, Proxmox, Mirrored SSD-Bootdrives/Pooldrives for VMs with a Containered Jellyfin 10.10.7 and an Arc A310 GPU with PCI Passthrough GuC/HuC enabled but no resizable BAR (memory limited to 256MB). I switched from Selfsigned certs to LetsEncrypt during that move and exchanged traefik for nginx proxy manager as my reverse proxy. HW Transcoding seems to work (got 445FPS for a HEVC 1080p -> x264 1080p). Even the Intro detection for the skip button works.

The Problem:
The AndroidTV with the Jellyfin App stops playing a video file roughly every 10 minutes. It warns me with something along those lines: "Something went wrong. Retrying". Then it starts playing the file again after a few seconds at the point where it left off. Sometimes, when i jump 15 seconds in any direction, it took longer or might not work at all. I have to stop the playback and play it again.
However, before my move to the new hardware i have not observed such a behavior. In contrast to that, playback via WebUI (i.e. Safari and Firefox) works fine for the videos in question.

Setup:
Hardare: Xeon Silver 12C 24T 2.1Ghz; 128 GB Ram; Intel ARC A310 (GuC/HuC enabled) No Resizable BAR.
OS: Proxmox 8 as HV; Debian 13 (Testing) with Linux 6.12.27-1 as Guest. GPU is passed through.
Docker: 28.1.1, build 4eba37
Jellyfin docker container: jellyfin/jellyfin:10.10.7 
Reverse Proxy: docker.io/jc21/nginx-proxy-manager:2.12.3
client: Jellyfin for Android TV
client_version: 0.18.8

I attached the logs from the server, a crash report from the AndroidTV app (might be the wrong one though, it's the only one I got) and the FFmpeg logs. 

I am not that deep into that matter, so please be patient with me as I do not really post anything that often. But am thankful for any hint and love the exchange with you all :)

[besenwesen]

A thing that could lead to the source of the error:
Can it be that when muxing two files with ffmpeg (separate audio and video stream files) together, with unequal length, that the player might not be able to handle the playback correctly? It's the only explanation I can think of, since other files work flawlessly.

E.g. ffmpeg -i video_audio1.mp4 -I audio2.mp4 -map 0 -map 1 -c copy video_audio1_audio2.mp4
with ffprobe video_audio1_audio2.mp4 I can see the length of the video stream, but not the length of the audio streams. Any idea?