Lo que me huele es que el motor está estropeado, la verdad. Prueba a ver si una hélice cae más que la otra y si es así, cambialo por otro motor 😉 Te dejo un tutorial que hice: https://www.youtube.com/watch?v=_gBfrCVRfkU
I assume that it does fly, if it does not take off, would it not be best to rertun it. Something that I would have a try at, is lubricating the main drive shaft gears, with a light white grease and maybe a drop of oil in the top of the two shafts. As you can see in the comments this has been bought up. Hope that you soon have in flying right.