When adding a user to the AD-hybrid user group, the property “Username” will no longer accept the hyphen character. I think this behaviour occured after upgrading to 7.6.3.
As you can see from the attached pictures there are already users present that use hyphen character. These were added before upgrading to 7.6.3.
[attachment=1]untitled.png[/attachment]
[attachment=0]untitled2.png[/attachment]