Know of someone who was in a heavy jet and had a hold slapped on them very quickly them in the cruise. As they turned downwind and still getting their act together they almost stalled the thing; had the shaker going off and lost a few thousand feet in the recovery.
I obviously wasn't there so I'm not saying it happened like this but it is worth thinking about..... Many many airline pilots think that the top of the lower amber band that provides them 40 degrees bank to stick shaker, implies that as long as they are above that speed, then they can safely bank 25 or 30 degrees into a hold, at altitude, and expect the aircraft to maintain it's height and airspeed and fly around the hold no problem. There is no such guarantee. I personally think that, or a windshear, or both, are the most likely culprits for your scenario.