Opening a file results in a blank code page displayed. Display view is fine

I have been using Dreamweaver for many years and for at least the last year, maybe more, after I've opened a few files, and worked on another app, upon returning to DW, opening another existing file results in the codepage being blank. The display view is fine.

I can open multiple files, 15+, without issue if I open all at the same time.

When the issue occurs, the actual DW window is truncated on the right side. The right 1/3 of the header bar is missing (ie I cannot see the min/max/X buttons) and I have to click File|Exit to close the window.

The files I open are typically HTML or JS.

I have reinstalled Dreamweaver  (V21.4 build 15620) and reset preferences to default but still the issue occurs. If I close DW and reopen the file, it's fine.  

I'm running on Windows 11, 64bit, with 16gb Ram.

I hope someone can help as this is soooo frustrating!!