What is the MCC_CGP pcb? Is this the main pcb for the SLC(single lift computer). From what you have said, you have isolated the calls from the from the shaft so to me it can only be the SLC that is generating these calls. Have you disconnected the complete chain that goes down to the car calls? If not I would completely disconnect any and all down chain equipment (for the calls) so as really know where this is coming from, and see if these calls come in again. Then you can go back to the manufacturer with more info on the how it all works software/hardware etc.
