This is an odd one. Since updating Muse my master page now has a dashed line on the footer. Look at the screen grab - I have switched off all the layers yet it still shows. Any ideas?
Does it also show while you preview the site?
Can you try doing a Ctrl+A and see if that gets selected?
Also, check if you have applied a stroke to your Master page?
shows on preview and has been published. It will not select and I have not applied a stroke
I tried deleting more pages but Muse kept crashing
I found the culprit.
It was embedded in a graphic style which you have applied, see below for reference;
Remove or replace this with any other and your issue with be resolved.
Hope it helps.
Fantastic that was driving me demented! Much appreciated