This photo shows T1 decoder with short harness installed in Atlas Train Master. The NMRA plug needs to installed as shown with the Red and orange wires facing towards you when plugged in. Notice the harness wires are folded back. Do not not bend wires at point they are soldered to NMRA board. They will break off. Form bend of wires away from NMRA board as shown in picture.
Do not bend here. Form bend here.