Closing a bubble door in a bell medium while in flight is sometimes not an easy task. Many Bells require 2 hands to close the door when sitting on the ground, never mind while in flight. In flight the bubble act like a wing and at 60-80 kts the door sits 25-30 cm open and stays there.
Your speed in most bells needs to be less than 40 kts to get the center latch to close. If you also want the top latch to close, the airspeed needs to be very low, uncomfortably low for no hands flying anyway.
At 20 ish kts, one hand on the latch, body leaning and twisting so you can get the other hand on the strap to pull in the top of the door, cyclic between your knees....problem is when you twist to look up at the top latch and struggle with it for a few seconds its easy to loose peripheral vision of the horizon. With no hands on the cyclic and no eyes on the horizon the nose comes up pretty quick. Look forward and see nothing but sky grab the cyclic in a panic.....
We will never know exactly what happened that day, could have been a medical issue...could have been some variation of the above.
The door closure system in many types of helicopters just plain suck when you think about it.