Page navigation block is hiding the instrument panel

Hi. Just noticed a bug. When I use the page navigation block and it is set to 0px sticky margin from top, it is hiding the instruments panel. Please take a look at this short video with the problem – https://u.pcloud.link/publink/show?code=XZONigVZNRJwIhYxOnuzRk7MNr0Vd06sRtjy

Also I constantly receive the following error: “Update failed. The response is not a valid JSON response.”

Please advise how to solve these problems. Regards