As you observed in comment #1, this is because disassociated radio buttons are not properly grouped and thus automatic unchecking never happens: bug 1685926. Let's track this there. (This adds a real example, thank for reporting!)
Bug 1699378 Comment 3 Edit History
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As you observed in comment #1, this is because disassociated radio buttons are not properly grouped and thus automatic unchecking never happens: bug 1685926. Let's track this there. (This adds a real example, thanks for reporting!)