Brushcutters

I have a Huskvarna 335 FR Brush cutter, and the power head has rotated app 30 deg around the shaft- is this a real problem, and what is the fix?

Is it a loosen, realign, retighten operation? If so, what needs to be loosened to make the fix?

Or is there some kind of key that is supposed to hold the power head in position? If so, what is the part number for the key?

Thanks,

Spiceman