out of all these posts nobody has mentioned checking the battery voltage, this should be one of the first things to check when errors start popping up. These trucks are VERY voltage sensitive and a faulty or low battery can make one code out various codes.

now with that said, i know these trucks had problems with the height encoder from day one, first they updated the encoder itself and then there were problems with the wiring harness @ the encoder, this was updated also. I would verify that the problem with this next. If you find wiring issues repair as needed or if no problems found in the wiring? replace the encoder.

as for the sister truck stuck in creep mode?
do as was suggested, check the 24" sensor at the base of the mast and make sure it is operational, it has an ORANGE light on it and when platform is lowered it should be turned on. If you see no light check it by putting something metallic in front of the switch as it is magnetic and should turn on. If you get no light still? then you have either bad wiring, connection or just a bad sensor. Repair as needed according to what you find.
In my experiences with these you may find it is just an adjustment but if you have any doubts about the validity of the sensors operation replace it.