You might want to take a look at subform/field bindings, and initialize events.
If you have a binding to a repeating element, check your scripting and initializations.
It may be that you are appending to a structure each time you initialize the form - even if it already exists.
I have reviewed forms that had subforms set to repeat based on binding to elements, and a script that was adding an instance each time the form initialized.
Not saying that's happening here - just throwing it out there.
Sounds like you have narrowed it to the radio buttons - good luck
Mark