Hi these MTH Z4000 transformers can be repaired the bad thing is there very expensive to ship!
you may have a bad power supply, I repair these where do you live which state as George stated a gear could be out of adjustment but you have to be very careful taking those transformers apart or you can damage the boards wire harness is easily be pinched when putting back together !
if you're coming to York you could bring the z4000 there could save you on shipping and not getting damaged in shipment!
Alan