i'll assume this is an orderpicker?
it probably has steering sensors or an encoder on it and one of the steer limit sensors is off or the encoder is bad.
other than a bad encoder there are also thing like if it has an encoder how is it mounted? or what connects it to the drive unit? is the connector tight on the encoder shaft? Things such as this can cause errors.
Just a couple of things to ponder while troubleshooting :o)
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