Cannot change width of the theme when editing layout

[Ellison Stephenson]

I have created several layouts - apparently successfully and they display and work OK - but

suddenly, when I proceed to edit the layouts, the theme background and margins are stuck at a position much narrower than the displayed width and and I can no longer drag it to change it.

I can drag the length up/down OK but the width is stuck (see attached screenshot)

 

This used to work fine but has recently got stuck.  The layouts still seem to work OK but the editor has this problem.

 

 

[Ellison Stephenson]

Answered my own question - un-tick 'view/page margins' in layout mode

I don't remember ticking it in the first place though ??