What would cause the left rear and right front calliper to stay locked up.

Typically, in modern vehicle braking systems, dual chamber master cylinders have a chamber that services the right front and left rear, and a chamber that services the left front and right rear. In theory, if one of those chambers had a concern, it could result in the diagonal half of the braking system to malfunction. Because you are having this concern, I would suspect an issue with the master cylinder or possible the hydraulic control unit of the anti lock braking system. Testing is highly recommended to determine what is going on.