Why can freezes occur when watching offline high-definition video?

Question

Video cards

When watching high-definition videos, such as .mkv, which weigh 2 or more gigabytes, friezes often occur.
At the same time, this moment is clearly captured in the task manager. There, the load on the GPU sometimes increases up to 50%.
Also, along with the video, the whole system freezes, because even the mouse cursor does not want to move at that moment.
It all started after I assembled a new computer, everything was perfect on the old configuration.
Configuration:
Ryzen 5 1600 6 core (before: Phenom II X4 965)
Radeon R9 270X last firewood
8Gb DDR4 (before: 8Gb DDR3)
And standard HDD
Changed different players, k-lite, kmplayer, vlc and all have this problem.
I changed all the firewood, reinstalled Windows and 0 sense. What could be the problem?

Answer 1

But I don’t trust AMD, NVidea is closer to me (although, in fact, the CUDA library is additionally needed).