Steps to reproduce:

• Create 16 or more Versions in a Project and put the smallest one on the top (less characters):
  

• Edit the Affects Version/s in a issue from this project and try to put the first option (the smallest one) in the issue. It will not appear and you can't simply save the entered value:
  

As a workaround, you need to click out of the field to save the entered text. It will show one error but will work after erase one of the duplicated versions.