All sites broken after using Upfront Editor

I have opened a thread in the support forum concerning a minor problem I was having in Upfront, here:
https://premium.wpmudev.org/forums/topic/newly-created-pages-are-called-new-page-and-cannot-be-edited

Moments after closing Upfront all my site pages refused to open.

cPanel is showing errors on a new site I created last week.

Please help.