the helicopter had 9 on board it was designed for 15 with equipment
path was correct , the altitude probably not , it was bad weather and in the bad weather atmospheric pressure suddenly fall and in that situation altimeter show higher altitude. so i believe they were flying lower than what they taught they were flying.
performance , the helicopter was perfectly in it performance parameter and was able to fly higher as two other helicopter show that.
here one thing raise question for me , in television when they described the flight they said they entered the cloud and for reduced visibility they decided to raise altitude and when they went over cloud they saw one helicopter is missing , i believe the mistake was entering the clouds and deciding to raise altitude instead of raising it before entering it and virtually become blind