Complex sentence: In March 2012, TTC officials admitted that the door threshold incidents were the result of "teething issues" another issue that was acknowledged involves a short delay in opening of the doors when the train pulls into a station.
Split into simpler sentences: In March 2012, TTC officials admitted that the door threshold incidents were the result of "teething issues". Another issue that was acknowledged involves a short delay in opening of the doors when the train pulls into a station.