Bug Why is the button selection always moving for no reason?

I did not wrote even code yet and the selection color is moving all the timme to the highest button...
I know that you can change the selected button by pressing TAB on most windows and UI elements, but I do nothing and I had this "bug"? already on different projects earlier, but this here is a fresh new project with just a Mainmenu screen without any code yet.
THe buttons doesen't even have a fuction right now, they are just optical but its still going all the way up, no matter what button I click.
I made a red border as highlight and selection color for the buttons, and you should see in the video whats happening all the time with it:

 

[SOLVED]
Someone told me now in the Unity Discord, that "Navigation" of the button is causing this.
If a moderator sees this, he can delete this thread (please).