If there's a question of Date/Time question type in the survey and the advanced setting "Minimum date" or "Maximum date" is active (for instance just a year like 2000 but it's the same result with a reference to another Date/Time question) the "Reorder question groups / questions" function of the concerned survey just shows a blank page. As soon as you deactivate the "Minimum date" and "Maximum date" settings, it shows up again.

Steps to reproduce:

1. create a new survey with standard settings
2. create a question group with standard settings
3. create a question of "Date/Time" question time with standard settings
   Test the reorder function: it works.
4. activate the "Minimum date" setting (write 2000)
   Test the reorder function: it shows a blank page.
5. activate the "Minimum date" setting (blank field)
   Test the reorder function: it works again.