[otrs] Undo Required Lock

I would like to enable Required Lock on one of my Activity Dialogs. However, when I do opening the dialog locks the ticket and sets the Owner as expected, but if I click "Undo & close window" in the dialog window I get an Insufficient Rights error. The user has full rw access to the queue in which the ticket is located and the System Log generates no errors. CentOS 6.x OTRS 4.0.13 Appreciate any assistance. +Eric