Please, check the bugtracker. There was a bug fixed in hotfix no. 75:
Form components - 'Radio buttons' form component not working for certain numeric values
Using numeric values that differ only in the first digit (e.g., 100, 200, 300) in the 'Radio buttons' form component's options generated input elements with identical IDs. As a result, users were unable to switch between the options. After applying the hotfix, a unique string is appended to each input's ID. The issue occurred after applying hotfix 13.0.70 or newer.
If you are using version between 13.0.70 and 74, please apply the latest hotfix.