Steps to reproduce:

1. Try to import templates having set host groups - some existing and some not existing in target instance (origin and target are both 5.4.3
2. Try with checked "create new groups"
3. Try with unchecked "create new groups"

Result:
When checked, import fails when trying to create already existing host groups. When unchecked, import fails on missing host groups.
Expected:
Not trying to create already existing host groups.

Workaround:

Rename or delete existing host groups matching those in imported templates and try import then.