Header Disappears, white bar appears while scrolling

Hello,

I have been building a new website (not live) and have applied an 80% transparent sticky header through mystickymenu. My problem is that on all pages when I scroll down from the top slightly the header disappears and a small full-width white block appears at the top of the site.

When you scroll slightly further (about the size of the original header size) the sticky header applies and works as intended.

I have not edited any CSS code and I am using the free Astra theme, editing with the free version of elementor.

Any help would be greatly appreciated. thank you