Car takes a jerk between 20kmph to 40 kmph

My car takes a jerk between 20kmph to 40 kmph and when I push accelerator it makes a sound.
After that it drives normally
I did computer test for the car and it showed Accelerator Pedal Position Sensor is faulty.

But the mechanic says the problem is with the gear.
Kindly advise

Regards
Sayeed