Hubsan Q4 problems

[AaronB]

My mate has just got himself a Hubsan Q4 and its been fine for a few days, but now when ever yu throttle up the front left rotor seems to slow down and it flies off forwards/diagonally.
Tried re calibrating the gyro and the sticks but it still does it??

Any thoughts guys?

Oh and this is my 1st post in about 4 years, had to start a new profile as could not for the life of me remember the password