I can’t engage AA, the check box is empty but gray. I have had this happen AOV’s where corrupted in the render layers panel. I would just go in, delete all the rules or keys and then AA would become available again. But now the Render layers are empty. Nothing to delete. I am in Maya 2020 with the latest updates for vray 5.
Are you talking about the “AA Filter”? How exactly do you reproduce the issue (a short video would be helpful)?
To my knowledge you can’t apply AA filter to Object ID render element (?), though you can too Material ID.