Got a Tekin 2050kv RX8 combo on my serpent 811be

Everything set up perfectly, solder on great. Motor does not run if I plug in sensor wire. Tried replacing the sensor wire but still same. (servo works with it plugged in but no throttle) If I take it off the wire, motor runs... any help would be appreciated.

FYI

I setup the same on my Losi SCTE 4600kv rx8. w/ sensor wire (works fine)

Both cars on programmed to my Spektrum DX3s