Re the AR One, although I don't have a schematic close at hand, I would would have to imagine that there's a trace that should line up between the two, which would line up between the two pin sites, and see if the trace on the board of the main unit is intact. If it is, then possibly one of the pins is not seated well, or the contact is dirty. Spray a little deoxit on the pin(s) & re seat them, and that might solve the problem.
I know that when I put the remote head on, and removed the main head from the radio, I found a lot of nastiness at the interface that had gotten in because or a torn gasket. Cleaned that out before completely separating the unit, and found the remote head functions were much more stable than the function operations of the original head unit.
Hope this helps!
