The truck gets it's height information from an encoder called ECR?mounted on the mast. This is a sensor with a wheel on it that spins as the mast goes up and down as it counts the length of raise. Then there is a Height Reset Switch called HGTRS1 which when activated, it resets the mast to 0 counts on the encoder. This switch is just a Hall effect sensor that picks up a steel weldment on the mast. Both of these are mounted opposite of each other on the top, inside of the outer mast channel. There might be a free lift switch also called FLS that is mounted on the back of the fork carriage behind the reach assembly which tells when the forks are above free lift. That switch could be your culprit. It would keep your fork indicator light at a raised position when they are all the way down. This switch is an industrial switch with a swing arm on it that is triggered by a weldment on the mast. As far as the tilt error, I know there is a pressure tranducer mounted on top of the tilt cylinder that could be bad. Also there is either a tilt position switch or a rotary sensor for the actual tilt position. I would have to check a truck at work. I have 2 of these at my location left. They are buying the new RMD6000 monomast trucks now..