I found my problem to be a conflicting plugin that caused this error. Namely, Woo Commerce Store Exporter – by Visser Labs. Disabling that plugin allowed me to create/edit fields and have the groups display on the backend editor.
To check this issue quickly, I would disable a plugin, then edit a field group, export that group to json, open it up, and search to see if operator: “” showed up. If it did, I would disable another plugin, and edit the field group again, and export, view, etc. When I arrived at operator: “==”, I knew I found my culprit.
Edit: Store Exporter Deluxe is the plugin.
