The red wire carries one of the power wires to the gearmotor mechanism = so you undoubtedly found the problem. When the relay clicks on it essentially shorts the microswitch providing the alternate method of powering the gearmotor (to get it started until the open microswitch takes over).
As for positioning on the activation track section, if the relay clicks but you get no gearmotor motion, check for clean wheel/rollers and center/outer rails. If the relay does not click, check for clean slider-shoes and the 4th/5th rails.
