There appears to be an issue with the text editor in GP Sections that was introduced with WordPress 4.8.1. When you click on the text heading dropdown in the visual editor (i.e. Heading 1, Heading 2, etc.) the arrow changes from down to up but the choices are no longer visible. It appears to only happen with text editors that are in modals like in Sections; the issue also came up in Beaver Builder and they just issued a patch that fixed it, referencing the ‘text editor z-index change in 4.8.1’.