Just recently bought one of thease scales s/h which would not function when first setup would just display error 1 message however after inspecting internal calibration weight & boards and re assembling the scale came back to life and will now read weight and complete Internal calibration procedure but if a weight is left on weigh pan over time the display weight reading keeps dropping and continues to drop until re-zeroed, has anyone knowledge with thease scales and what fault could be and cost of fault thanks.