When you Assign a record to another user who belong to another business unit which you don't have the Read privilege, from the form using the Assign button in the ribbon, the record is assigned but the user gets a credentials error.
I know this is by-design.
BUT, It would be nice to have an option to avoid the error when you "Assign" from Ribbon.
e.g.: option which enable to the Assign button to load a view after action is done.