Black Screen when playing media on Roku App

[harexew]

Im trying to play my media on a Roku Express, using the Jellyfin app. My server is running Version 10.8.9 on Windows Server 2016.
Everytime I play some media it only shows a Black Screen, on other devices (Firefox Browser on Windows 11 and Jellyfin app on Android TV) it plays without any problems. The only solution that worked for me temporatily is to run the files through ffmpeg with the following arguments.

Code:

ffmpeg.exe -i old.mp4 -c:v libx264 -crf 18 -preset slow -c:a copy new.mp4

The old and new files dont really show a difference in the media info screen.
Old File:

Code:

Video
Titel 1080p H264 SDR
Codec H264
Codec-Tag avc1
AVC Yes
Profil High
Level 31
Auflösung 1920x1080
Seitenverhältnis 16:9
Zeilensprungverfahren No
Bildrate 23.976025
Bitrate 708 kbps
Bit-Tiefe 8 bit
Videobereich SDR
Video range type SDR
Pixelformat yuv420p
Referenz-Frames 1
NAL 4

Audio
Titel AAC - Stereo - Default
Sprache und
Codec AAC
Codec-Tag mp4a
Profil HE-AAC
Darstellung stereo
Kanäle 2 ch
Bitrate 71 kbps
Abtastrate 48000 Hz
Standard Yes
Erzwungen No
Extern No

New File:

Code:

Video
Titel 1080p H264 SDR
Codec H264
Codec-Tag avc1
AVC Yes
Profil High
Level 40
Auflösung 1920x1080
Seitenverhältnis 16:9
Zeilensprungverfahren No
Bildrate 23.976025
Bitrate 1657 kbps
Bit-Tiefe 8 bit
Videobereich SDR
Video range type SDR
Farbraum bt709
Farbübertragung bt709
Primärfarben bt709
Pixelformat yuv420p
Referenz-Frames 1
NAL 4

Audio
Titel AAC - Stereo - Default
Sprache und
Codec AAC
Codec-Tag mp4a
Profil HE-AACv2
Darstellung stereo
Kanäle 2 ch
Bitrate 48 kbps
Abtastrate 44100 Hz
Standard Yes
Erzwungen No
Extern No