Supplementary information:
The only thing I can think of that might have caused the issue is that I edited a TEXT WIDGET.
From the Dashboard / Appearance / Widgets it is essential to Enable Accessibility Mode.
Then if I click on one of the TEXT Widgets I find that am unable to Edit the text. All I can do is change the position or delete.
So, instead I clicked on “Manage With Live Preview”.
When I did this the live preview screen did not scroll.
I assume this could be the source of the issue.
1) Could this be the source of the issue?
2) Is this functionality part of the Catch Evolution Theme?
3) How do I get it back to how it was before?
4) How do I edit Text Widgets in future?
Many thanks again,
Finn Jackson