4k content does not start on Shield TV

Good morning/afternoon,

I have a very odd issue that I can’t resolve. I have multiple Shield units, all of them can connect to my Plex server and play content, whatever the format / resolution / audio format.

All except one

I can’t figure out why, but for this very specific unit, it does connect to the server (hosted on a synology), browse the library and playback fine HD content. But if I select 4k content (which is visible through the library), it starts with a black screen and a spinning logo forever.

It happens whatever server I use (I have two Synology - used servers on each, I also tested with the Shield PMS running on the exact same Shield that is exhibiting the issue).

4k decoding does work, since I can connect to my NAS using SMB and Kodi, and playback manually the file.

It’s just 4k content which simply does not start, and only on this specific Shield unit.

I did perform a full factory reset, just to be sure, this did not resolve the issue

Any pointer would be welcome

Regards

4K + TrueHD?
Can select down to an AC3 track?