M20+ with R9; won't reverse

Bought a HS12 , R9 and two R12 at the fair in Dortmund. Put the new truck i'm building for a friend on a R12 and set up the transmitter, all works well. Put the R9 on an his older truck with a M20+ and SMX and tried to set up the HS12.
Everything works except one side of channel 4. So i can put on the lights, blink to the right and put him in forward drive, can't blink left, use hazard lights or put drive back in neutral or reverse. Tried the R12 witch works ok in the new truck, same result.
Tried my own HS12 with the R9, same result. When i put back the old receiver ( carson 10 channel ) and the transmitter Carson ultimate touch 10 channel everything works fine. The previous owner shortened the servo cables both on M20+ and SMX.
Don't think this is a problem because everything works fine with the Carson. On the Carson transmitter the throttle channel is trimmed because the truck starts driving when stick is in neutral. Had to trim the HS12 too for that reason.
With the HS12 and the R9 or R12 there is also a rattling noise to be heard that isn't there with the Carson configuration.

Thanks for the quick reply Jörg.
Problem solved by changing the settings as you suggested.

Great team you have there. Many thanks
Peter