The issue manifests under IE and Firefox when you change the selected radio button. It stems from any other control with RenderMode=Lightweight that brings the font icons the lightweight mode brings.

Workarounds:
- use the same render mode for all the controls (for example, move the form decorator to RenderMode=Lightweight)
- OR, add the following CSS rule to your page to remove the font icon content from the radio buttons
        .RadForm .rfdRadioUnchecked.p-i-radio:before,
        .RadForm .rfdRadioUnchecked:before,
        .RadForm .rfdRadioChecked.p-i-radiobutton:before,
        .RadForm .rfdRadioChecked:before,
        .RadForm .rfdCheckboxChecked:before,
        .RadForm .rfdCheckboxUnchecked:before {
            content: "";
        }