KS7000 File playback does not work properly

[redart]

Hello,
After receiving my ks7000 a couple of weeks ago, volume was unresponsive and menus very laggy. After updating to 1165 firmware, everything seemed to work fine. Until i tried to play some video files with the built-in media player. Most h264 .mkv and .mp4 are ok. But one h264 and all h265 .mkv/.mp4 begin to play with a dotted loading circle stuck in the middle of the screen and after a few seconds playback stops.
Demo 4k hdr or sdr files, play perfectly though. Tried the same files that i have problem with to a KS7000 at a shop nearby and play flawlessly. I already tried factory reset with no results. Any ideas please? Could it be harware related issue?
Many thanks

[zoelechat]

Well I think at shops they have TVs playing everything for demonstration, and they sell limited ones only showing circles