Flight mode changes to manual when throttle is advanced

I’ve been trying to program a APM 2.6 ( reflashed to the latest firmware) using my DX7 transmitter. All settings seems ok…modes will change when selected, flight controls all appear to react properly depending on which mode is selected…until I increase the throttle. The mode then changes back to manual and the flight controls remain in their last position. This also happens if I switch off the transmitter. An example is if I’m in STAB mode and I turn off the TX, the throttle advances to the preset value I’ve programmed, and the mode goes to manual. Essentially sending the plane into the ground. ANY help would be greatly appreciated

Are you sure your fail-safe is set correctly on your transmitter? When a DX7 is turned off the DX receiver will output whatever values the transmitter was set in when it was bound. Sounds like your transmitter was set to manual when it was bound and you’re having receiver problems.

The scenario has changed a bit. l now have a DX8. It seems that the only issue remaining is that the throttle still doesn’t advance in failsafe. Monitoring the inputs of channel 3 shows the throttle pulse width within failsafe ranges when the TX is switched off…and the mode changes properly. The output of channel 3 shows about 75% with no throttle advance. Could it be as simple as throttle lever position during binding? I have to admit I’m getting a bit confused at this point. If you could go over the Tx procedure briefly it might help.