If the bars are constantly flickering that this means something is likely interfering with Propo. Apologies, I do not have a DX6 - but it seems like filtering the levels on the controller should be the next step.
I'm not sure if it is called a _deadband_ but essentially what needs to happen is the control needs to even out any fluctuations in each channel that are within a certain range. I know for my Turnigy 9x I needed to have an allowed range of ~5 in order to avoid drift or bad input.
I'd start looking more into the controller - and then check there aren't any other drivers at play that could be messing up the Propo connection.
Viewing post in Rudder pulls to the right when flying on freerider
Forgive if I'm asking too many questions. I have 22 years of RC experience in Radio Control Car racing. I'm not familiar with drivers in my controller. I didn't even know that controllers had drivers. How would I find the drivers on the DX6 controller? Or any type of controller? Maybe I could go to Spektrum and ask this question and ask what type of setting do what to which controls. I know there is a sd card slot in my DX6 so I don't know very much how drivers work in a controller. I have been envolved with RC long enough when I used crystals and analog radios. So drivers in a controller are a new concept to me. Can you show me how to access them? How would you adjust filtering as well?