Dx6i throttle stuck on full

[cosmo99]

Hopefully someone has an idea on this problem. I'm connecting my Dx6i to FMS using Smartpropoplus via the mic port on my laptop using a stereo cable. When I view the inputs using PPM Thermometer, all of the channels look clean and they respond to stick movements. When I try to use FMS, the throttle is stuck on 100% all the time. When I change the Gear / F Mode switch, channel 1 in FMS changes. But this doesn't make sense because the Gear / F Mode switch is channel 5 in PPM Thermometer. It's like FMS is mapping channel 5 audio input to channel 1.

I tried to re-calibrate in FMS but the throttle channel (1) never moves off 100% even though the PPM Thermometer is moving correctly at the same time. It's like FMS is not seeing the throttle channel input. Anyone have an idea what is going on here?

Thanks!
Mark