Can't edit relationship settings in studio

[MateoLeFou]

I had a problem with SOAP calls in another thread and have traced the pattern: Accounts that don't have any relationships with contacts are failing to return XML via SOAP.
So I went in the studio to refresh/revamp the relationships, but when I click on the Relationships icon it just fiddles around, says "Done" and doesn't change the display. Clicking on "Fields" etc. works fine.

[MateoLeFou]

Error console reports

Error: syntax error
Source File: http://www.example.comsugar/include/...-all.js?c=1%22
Line: 9, Column: 1
Source Code:
()