Upfront Theme Editing (bug) causing crash


while trying to edit the layout of the main nav in landscape tablet mode, I am getting a crash of the editor widow whenever I attempt to move either the title or the social elements. This is making it impossible to achieve a good looking layout for me, and the crash seems to persist through toggling responsive on and off and can only be resolved through a full reload of the page.

The detour window remains, but the controls and editing functionality is removed as per screen image supplied.

Please advise.