I believe this is because of your XPath filter in the mapping:
<my:RepeatingGroup>my:UATForm/my:QuestionsGroup/my:Questions[Question !=""]</my:RepeatingGroup>
You don't have the "my" prefix on Question, thus, there are no items to submit.
<my:RepeatingGroup>my:UATForm/my:QuestionsGroup/my:Questions[my:Question !=""]</my:RepeatingGroup>