How to solve header's height adjusting glitch on 7.1?

Site URL: https://banjo-recorder-36fe.squarespace.com/quem

Hi there!

My still in development website is presenting a strange behaviour. Whenever I reach the top of the page and stop, the header adjusts a tiny bit its height in direction to the bottom (expands vertically). I can understand how this behaviour is occurring and it is oddly annoying.

Can anyone please help?

Hi. Your site is private. Can you setup password & share url again?