you could have been over driving the receiver when you walked up to the airplane causing the servos to twitch harder...this is normal
now the orginial problem..do you have dual aileron servos or just single? when you changed batteries did you go from 4.8 to 6.0 volt?
and finally what happens when you do a range check at home then at the field?
You could have been getting hits from some park flier somewhere close....