I’m using the child theme of GeneratePress template (v 2.0.2) with GP Premium (v 1.5.6) and I have an issue with switching tabs in editor. If open text editor, can’t switch back to visual mode. In console is “TypeError: a is null” for tinymce.min.js (screenshot). Error exist in Firefox only (v 57.0.4) and is probably related to the Sections function, because editor on the page without sections works correctly.
I tried to disable all plugins and after disabling Gridable plugin error disappeared.