Hi, This form looks of 6.1 FP1. Anyway, Can you share the error also if any in console logs or error logs. It would be helpful in pinpointing the problem. Ideally, this should have opened the rule editor in 6.1 FP1 as it did for you the first time.
Also, were there no changes made to the form in between the rule editor working and broken state. Could you try to reproduce this with a new form and share your experience with us, if It behaves the same way. Thanks.