My father has a Blade 450X with the AR7200BX and when you go to take off with it off the ground and it is about to lift off the ground it will just like pop up and down by it's self and I can not figure this out. It does not have any vibration problems that I can find or feel, the AR7200bx is now on like 5 pieces of tape because I was trying to figure out if it was vibration that was causing it. I can not find any info about other people having this type of problem and my father loves this helicopter and this time I can not figure out how to fix it. This helicopter has been fine for years, he has crashed it a couple of times. I have repaired it and it has always flown fine after. It started doing this last summer and it was not after any type of crash it just started happening one day and he stopped trying to fly it. I forgot about it, and am trying to get it flying again. I do not know if like the AR7200BX just went bad or something changed or if he clicked something he was not supposed to. If anyone has any tips I would love to hear them! Thank you for viewing! This is my 1st post on here!