4K video - kills the UP Board


I have couple UP Boards - heat sink version. Whenever I play video in 4K resolution board freezes after some short time.
Tried official ubuntu build also upgraded to 4.11 kernel. Makes no difference after 15-20 minutes board freezes and
require hard reboot.

to play video I run X11 + compton composition manager + mpv with hardware decoding :
root@ubuntu:~# mpv --fs --hwdec=auto --vo=opengl 4K.mp4
Playing: 4K.mp4
(+) Video --vid=1 (*) (h264 3840x2160 29.970fps)
Using hardware decoding (vaapi).
VO: [opengl] 3840x2160 vaapi[nv12]

Have tried official build for all of the above as well latest versions from edgers/testers repositories. No difference.

CPU Temperature reading goest up to "75C - 76C" according to lm_sensors.

It does not really matter if video 4K or 1080P or lower resolution. CPU utilisation for MPV is 18-25%. Overall CPU utilisation ~ 20%.

Anyone experience same problem ?