Can't deselect answers in JAF in External Career Site

Hi,

we have set up questions on our JAF for external candidates on the External Career Site. We have used both prescreening questions and flexfields, both set as Single Answer for the question type. We have noticed that, both for prescreening questions and for flexfields, once a candidate has selected one of the answers, they can't deselect it so they can't leave the question blank even when the question is not mandatory. Does anybody know if there's a way to allow the candidate to deselect the selected answer?

I'll attach some screens to better show you the type of questions and answers: