Please use the survey navigation buttons or index. It appears you attempted to use the browser back button to re-submit a page.
I have tried using different themes, disabling Ajax, changing group names/id's nothing actually solves it other than have the questions set to all in one. Which I actually don't want.
I did put in a ticket about it, however i figured out myself that Firefox is actually causing the issue. Using Chrome instead allows for the group questions to appear on different pages.
Well no it is not a full solution because ideally you would want a survey to work with every browser.. So for me it is a small solution using Chrome so that my group questions can actually navigate on different pages.