There is a mechanical bind preventing the scale from freely settling to zero. Check for obstructions to the weigh scale and conveyor mounted on top. Ensure cables, desks and adjacent conveyor are not touching the scale. If the problem is not solved, try removing the conveyor from the scale base, calibrating the scale and then retest for performance. Note that the scale can be turned upside down so the scale feet are on the floor for testing when conveyor has been removed.