New in version 4.0 is a bug that causes all filters that search based on a Fix Version or Affects Version to be broken after the related version is renamed. This means that it is now, from a practical standpoint, impossible for us to rename versions.

Steps to reproduce:

1. Create a filter that searches for a matching Fix Version which is assigned to at least one issue
2. Using that filter returns the resulting matching issues as expected
3. Rename the Fix Version on that project
4. The filter will no longer return any results