Single choice unit moved > correct answer unchecked

Hi

I've got a unit with three single choice modules. Whenever I move a single choice module to another position within the unit, the correct answer of the module is unchecked and the answers are not shown in frontend. If I check the correct answer again, answers are displayed. Thanks, Marcel

Example: http://alltagssprache.ch/courses/sich-vorstellen/units/ling-fernando-und-lena/