I very well could be wrong but I am thinking that when you first crashed, near that other rc person, it somehow damaged your quad. I would check the balance and see how balanced it is. I would check the arms and see how straight they are, I would check the motors and see if they seem to be working the same or is there some slight different way some are working that might cause this. I realize that it most likely is a software issue, but since software shows no problems I have to think hardware. I think you said the issue happens no matter what setting you have and that you have tried manual mode and it seemed to do the same thing. If that is so I would look very closely at the body and everything else that could cause an unbalance. I am not trying to get you to waste time on something but I would hope that I could be right and you would be flying sooner. keep us posted
or.. thinking about it. If some computer part failed when you were flying in the park and caused the crash that you thought was caused by another rc user. It is possible, and to clarify.. you were flying, something failed and it is still failed. I guess the route you are going should address that.