Spektrum AR9020 values jumping around


I am running a Spektrum AR9020 receiver on an Pixhawk with latest 4.0.3

I am getting unreliable RC connection. Specifically the values of some of the channels are jumping around erratically without any input on the transmitter. Also i am getting signal input on channels 10/11/12 although the AR9020 only supports 9 channels.

I have connected the AR9020 to the pixhawk using the SXRL port of the receiver and the RCIn port of the pixhawk.

Am I doing something wrong?