Main Nav – jumps up

Hi,
Is there some way to stop the main nav from jumping/bouncing up every time a new page is selected?

The Feb. update is when it started, and I used the following code:

.sticky-disabled header{ top: 0;} /*should avoid the header jumping if not logged*/
.tc-sticky-header #tc-reset-margin-top{ display: block;} /*reduces the content jumping*/

However, with the latest update 3.3.26, the code is no longer effective.
Any help is appreciated.
Thank you,
Suzabelle