Hi,

I think what’s actually happening is that focus moves to the Edge menu control. If so, press F6 to move to the document window.

Cheers,

Joseph

Adrian,

           Consider:  Using SFC (System File Checker) and DISM (Deployment Imaging Servicing and Management) to Repair Windows 8 & 10

           These sorts of completely atypical issues in anything shipped with Windows strongly suggests an underlying corruption, somewhere, and who knows where.  Those two utilities repair same, and harm nothing, so they're a good place to start.  It may or may not work, but at least you'll have more data.
--

Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042  

One does not discover new lands without consenting to lose sight of the shore for a very long time.

           ~ André Gide