Version field incosistency - GreenHopper and JIRA

Using a card view for planning board - GreenHopper allows editing version (fix version) for an issue.

This is a dropdown box and shows / allows only one value (based on the filter). While if the issue is added / updated through JIRA allows multiple values.

So when the version field gets updated through GreenHopper it corrupts the value for version.

Is this a configuration issue or a Greenhopper bug?