In the data model viewer, when the lock is clicked it blocks the objects, but when you leave the data model viewer to go to the sheet for example and then go back to the data model viewer, the lock is still selected but the previous configuration is lost and goes back to the original position.
Qlik Sense November 2020
This is a know product defect with ID QB-4205
Information provided on this defect is given as is at the time of documenting. For up to date information, please review the most recent Release Notes, or contact support at support.qlik.com with the ID QB-4205 for reference.