Was on an easy jet flight the other day that had successfully pushed back and was taxiing to the runway when the captain came on the loudspeaker and announced that we had to return to the gate due to a fault having been discovered with the pushback tug. As such we returned to the gate to allow checks to be performed to the aircraft.
What I was wondering is what could be the reason behind this - as I said the aircraft had pushed back successfully and was moving under its own power - obviously part of the operating procedure before start of taxi is for the dispatcher to show the pin to the pilot to show that it has been removed so can't be this - what else could have been wrong to necessitate returning to the gate and requiring 20 minutes of checks and only been identified a fair time after starting taxi?
Would be really interested if anyone has any insights / thoughts

The captain was probably busy dealing with the problem and did not tell you the whole story.