Wicket has a 'bug' ( https://issues.apache.org/jira/browse/WICKET-2393 ) which does by default trim PasswordTextFields (Or any Textfield in this respect ).
For Gitblit this means that a password with spaces at the end will not work.
Because this only affects the UI but NOT the git protocols, I would suggest fixing this 'hard, so gitblit would behave with all access protocols the same way.