Hi - I've been trying to troubleshoot this all day, as this particular page has been giving me the problems.
I haven't added any new plugins, plus this had previously been working fine.
There's no cacheing plugins running. And I deactivated jetpack.
PHP is version 7.0.6
The problem as far as I can tell (on this page) occurs when I only use CLASSIC SECTIONS within this page. As soon as I add a new non-classic section and save. The console starts working again.
I rechecked other portfolio items pages that have the same method for getting slider to go 100% of container. I can edit these in the console but to my surprise, there are only classic sections and rows being used. I thought I might have figured it out, but this doesn't make sense if other portfolio items are fine with only classic sections.
I have migrated the site recently using updraft. I don't think this is an issue as I was able to edit in pro after the migration.