Yesterday's YYT-YYZ AC127 went mechanical at YYT. Scheduled departure 12:05 and eventually cancelled at 20:30. We were given rolling updated delays and new departure times. Returned to gate twice. Crew went out of hours and a relief crew appeared, except for one person was missing so flight was cancelled.

Captain said a sensor was the problem but no further technical information. This may have related to an engine as engine runs were performed and a high speed taxi was done during the day after we had been offloaded for the second time. Captain also said that the sensor may have been impacted by slush as they approached the gate on inbound arrival.

Out of interest, does anyone have information on what actually happened?