Probably, cleaning was all that was needed. Reassembly needs a little care to ensure that the shims (if any ) and gib strips are replaced correctly, so that the grubscrews locate in the holes…
Sometimes, for some unknown reason, either the readings remain fixed, whatever the jaw position, or are absolute nonsense.
The instructions say that if this happens, remove the battery, wait 30 seconds and then replace, and operation should be normal again.
Mine came, YEARS ago from LIDL, and are falling apart (Thumb wheel missing,, battery cover held in place with an O ring, but still functioning. )
Howard