Stannah 400 stairlift?

Changed batteries as chair slowed down after half way up stairs, Found loose yellow/black tracer wire and chair seat now rotates anti-clockwise before moving up.Moving down it rotates back to normal and descends OK.
The twelve way plug/ socket has 12 wires one side but end mauve in wire has no connection on other side. Is this where the loose wire has come from

Mike
February 2013