Minivator Simplicity 950+ displays error code 3 at top of rail?

Error code 3 showing at top of rail and powered swivel not working on Minivator Simplicity 950+ (or 952 ?) stairlift. Any advice and/or schemeatics/circuit diagrams would be greatly appreciated. (Have looked for reed switch and magnet shown in previous info I obtained but cannot locate these, have they been replaced with microswitches or other devices ?).

Dave W
July 2018