Have a 1978 Schindler/Haughton that will not cancel out the top floor call. TC stays latched and car call button light stays lit. Have gone thru every single contact and relay. Button is not stuck. It's not residual magnetism on the TC relay armature. Changed the stepper board, still nothing. Every once in a great while it will cancel. All relay sequences look ok. I am baffled. Any ideas. car will leave floor to answer other calls, but call stays in and car always returns. If you kill power the call will drop out and stay out until you put it in by pushing the call button or setting it with the relay at the controller.

Is it just the car or hall call too?

I would probably change the TC coil (set reset). Is there voltage on the coil? Also, maybe replace the lamp in the top floor PB fixture. Did you take the wire off in the machine room coming from the button?

check the upper and lower hatch switches, normal and such. If one is bad, top or bottom, the other is soon gonna be bad.

Is the FX relay at that floor working? Some jobs used FA relays but the FX relay contact has to make to pick a CC relay which in turn fires TR and cancels the call. The call circuit is just a self holding contact through a 47 ohm resistor on the timer display board. To cancel the call you first need the associated FX relay to make up.