This issue occurs when using the touch/onscreen keyboard. If you use the touch keyboard to type into a webpage search box, when it loads the new page (eg. search results) and you begin to scroll down, a blank space appears equal in height to the keyboard obscuring the bottom of the page.
The only way to remove the blank space is to go back to the search field that caused the issue, invoke the touch keyboard, and then close the touch keyboard.
This behaviour is present in Edge Dev 80.0.345.0 and I believe it began with the previous build. I've also checked and it occurs with the current Canary edition too. I'm using a Surface Pro 6.