If you look inside your transmitter case you may not see any obvious binding and you will close the case thinking everything is fine. On closer inspection you may find, just as I did, that in some transmitters the wire bundles connected to the sticks are cut too short by the manufacturer and do not provide adequate strain relief. At least one wire will eventually fail due to low cycle fatigue (bending it back and forth). Sometimes the wires may not be properly restrained (clamped) and suffer the same type of failure.
It sounds like the Futaba 9C is not exempt from this old problem.