hello I'm a jd owner and my jd and has not been working very well. when i first got it we were given parts because the on we got did not work and we thought that the problem was solved. my dad took it to his work to see if someone could do calibrate it for us. I thought that it worked but it would not walk straight or turn correctly. so I decided to re calibrate it but when i did it would all ways fall over when walking. please help i do not know what to do.