This is probably a duplicate of RT-11839, but I'd just log it anyway. WebEngine fails to render HTML radio buttons, as it fails to render HTML checkboxes in RT-11839 - for an example, see http://www.cs.tut.fi/~jkorpela/forms/choices.html. Similar exceptions as the ones reported in RT-11839 are thrown when hovering the mouse, where the item was supposed to have been rendered.

For a code sample, see RT-11839 also