create issue - version validation

Somehow the validation for the version fails everytime I create a new issue (see version.png). I have to delete the version in the corresponding field and retype it again so that I can create the issue.

If I delete the version and try to create the issue it fails as well (see version2.png)

However, if I create the issue and assign a version to it afterwards it works fine.

This bug exists not only in 5.1.7 but also in the version used on this server (see version3.png)