related thread can be fount here (bottom):
https://www.joomshaper.com/forum/question/2496#qa-answer-10398
So i startet with a new page. added rows only and the menu works under linux.
i added 4 empty rows. everything is alright last row i placed the image gallery. also everything is alright.
after that i placed a feature box on top of the page. and here we go, the menue jumping / flickering is back again.
maybe you wanna look at this.
EDIT: it's a screen size issue.
if i make the browser window smaler i also dont have that juming / flickering.