Steps to regenerate:
1.Open URL https://demo-trunk.ofbiz.apache.org/webtools/control/main
2.Navigate to Order Component.
3.In Order Manager, Click on returns.
4.Click on Create New Return.
5.Navigate to To Party Id field in Create Return Form.
6.Type any character or word in the field and try to select any party from auto-completer.
Issue: unable to select any Party from auto-completer on mouse click or Enter key (on hover,auto-completer results are disappeared.)
Note:I have seen this kind of issue on various places.
Here are some links for reference: