The TX16S is my current preferred transmitter, however it has an issue with the aux port for the head tracker, you have to pull the plug out slightly to get it to work and sometimes it will unexpectedly disconnect. This is a known issue but I have found a solution.
You can open the transmitter up and easily bend in the second tab from bottom of the auxiliary port as shown in the pictures bellow, this will ensure it connects when fully plugged in and will stay connected. This was a very frustrating problem so I am happy to have found an easy fix for it, if other transmitters have the same issue the solution may be applicable to them as well.
Medlin Drone 