I have noticed this over the years. Occasionally the header bar does not resize properly when scrolling back to the top.
I notice that on my site, the <header> tag gets assigned a height of 139px, which is accurate. But at times, it gets calculated at 115px.
This seems to happen randomly. I cannot replicate it consistently, but it does happen enough that I notice it.
Attached is a picture when it calculates to 115px and when it correctly calculates at 139px.
I hope you are well today and thank you for your question.
I visited your website and the header is resizing correctly for me without any issue.
Could you please test it on a different browser?
Also, This can be a child theme issue used on your site so to confirm it just temporarily use the Jevelin theme on your site. If everything works fine then it’s your site child theme issue.