Wide circular motion? Well, if you can return it, then do that, and see if you experience the same problem with a brand new one. I don't own this helicopter, but from what I know about similarly designed helis, I do believe you are correct; the (+)/(-) are probably the gyro trim (or gain, I can't remember if those boards have gain or not... - doesn't matter, at this point I would tinker with it, because it's not like things can get much worse).