SONY A6300 Horrible 4k Details And Pixelation

[Senhel]

Hello! I have such a terrible problem with my Sony a6300!

In details: I notice that something wrong with my a6300! When I record video in 4K XAVC (any framerate) and simply when I have motion in frame, video starts falling apart, pixelation appears everywhere, I feel like I record 480p but NO, this is still 4K!

I attach frame from video when this thing happening!
PLEASE HELP IF YOU KNOW WHAT IT CAN BE

https://1.img-dpreview.com/files/p/TS1600x1600~forums/61244796/dd8f216cb99d4870843e67b3137c5e0e
https://4.img-dpreview.com/files/p/TS1600x1600~forums/61244796/e1612a7f3202405e8f8e004ecdc096ec
 

[Makeev]

Please send a source in mp4 format. I will look.