Macbook Air 2010 trackpad stop working when touching case (palm rest)

My MBA 2010 A1369 had demaged keyboard and trackpad by liquid. I got used whoel top case and replace. (not myself)

Seller claimed it is ok but we face one problem. when I touch case (palm rest) trackpad stops responding. When on one side partly when with both hands then completely. Even when touching case from side. Even when case is comered by paper. So it strange behavior.

Both cases were from A1369 model but on mine was black plastic foil over part of keyboard while on other not. So I am not sure there could be some other differences that could cause this.

Would anybody has any suggestion where could be problem? Wrong contact bad insulation somewhere or faulty trackpad.

Thanks a lot.

Frantisek