Guys, does anybody know what's the cause and most important how to resolve that flick,
auto levels, auto contrast and auto color have been added to the clip,

levels - YouTube
thx!

Precisely these filters do cause the flick, since they are working on the frame basis level. Each frame then can end with a bit different color balance/contrast. Especially if the material is interlaced.

You can try adjusting "temporal smoothing" parameter to keep it more steady, but I'd rather advise you to use standard manual color correcting filters like fast color corrector, three way color corrector or curves/levels if you are not familiar with the first two.