Last button in sliding menu wont align

Hi,

I have a problem with the last button on the right side.
In the beginning (before hovering over the sliding menu with cursor) all the buttons look perfect, as they suppose to.
But after I hover over any button in the menu, the last button will return to its position bigger, as it is supposed to (4px wider from the right side over the edge).

If I hit refresh, it will be normal again.

I have checked many other sites with the same theme, they all seem to have the same problem.

Here is my site
https://www.andressoop.com

Any help is appreciated ??