I ran into a similar JS id issue yesterday. I was using a WSYWIG form builder that, for some odd reason, assigned duplicate ids to two different form fields. When I tried to publish the webpage, I got an error about the id not being unique. I found the duplicate ids in the source code and went back and deleted one of the fields with the duplicate id. I added the same field, only to find that the system re-assigned the same id again. I changed it manually, which you can do as long as you haven't saved the field. It's definitely a bug in our software, so our web development manager is going to contact the company.

Sounds like you did a great job trouble shooting. That process would take a long time if you didn't know that a duplicate id was the issue. I had the benefit of an error message but it sounds like you didn't. Nice job!