It seems to relate to when the program records the "forms in use" into the database that is used by the Group Select and Filters. This usually happens when you view forms, print, e-file, or update client database, but it seems that the calculation that happens during locking doesn't always trigger it. Unlocking and doing an update client database should correct that information, just verify that the form is in bold on the forms tab. Development is looking into something relating to locking returns and it may be related.