Sounds like the motor isn't tuned right. I had same issue were mine would lose power and fall no matter what I did alot of times when I would punch gas to full it would fall. But we had to tune it also check your head my head actually was lose and causing us not to be able to tune it right. When I said head I mean the motor head I brought my heli in and checked stuff on it and I could move motor head with my fingers
. So I fixed it but I have had about same your talking about when motor isn't tuned right. Sounds like it might be running a lean not sure.
If I could see the video's it might help me to help you tune it since I can see smoke etc.