Image problems in Octagon SF8008

Hi all!

I just got this receiver and I'm having a problem with the picture. The brightness changes randomly and quickly, from normal to dimmer/brighter to normal. This also varies with the content being played and is especially noticeable during football matches.

Has anyone faced this problem and if so, please let me know if you were able to solve it?

Thanks in advance!

I have tried 3 hdmi cables 2.0 and 2.1. Resolution 4k50hz. TV is Mi TV Q2.

The brightness just changes at random times for a split second, like a flicker. This is mostly noticable when watching football.

I'm also using Define OS 7.0

I have an old receiver which doesn't have this problem.

Just the default ones

Resolution 4k50hz
Auto frame rate Disabled

Colorsapce YCbCr 444
HDMI HDR Auto

HDMI CEC Disabled