Hello! I Have a similar problem. After a Server Migration and manual DB update, some part of Modules got Dropdown menues disable. If i try to Select a Source, i just can´t do it, because "Form Area" is Missing, as you will see in attachment. Also i have the Template GK News Template, but i just cannot edit Template Styles because all menus and Form areas are gone as well.
at Configuration Check: All is configured properly. I have the latest Joomla version, 3.7.0.