I spent as much time as I could at Lasham in 1958/9 learning to fly a glider (under Derek Piggott), and then working up to Silver C.
The smooth functioning of the gliding operation was interrupted at intervals by arrivals and departures of Dan Air Yorks. I cannot recall one arriving with all 4 engines running, although I suppose it could have happened. Sometimes there were only 2.
Departures after repair/maintenance were always exciting; usually two or three attempts were needed, separated by short hangar visits to rectify whatever had caused the take-off to be abandoned.
All the launching wires had to be cleared for these interruptions (2 winch, 1 tow-car), as well as any gliders parked too near the runway.
I really don't think you can use the words "reliable" and "York" in the same sentence.