I HAVE ONE DC MULTIFUNTIONAL METERS (SKU:200193) THAT I HAVE USED FOR CLOSE TO TWO YEARS. IT JUST STARTED REPORTING A -1.5 AMP OFFSET FROM ZERO. MY SECOND MULTIFUNCTION METER (SAME SKU) ALSO JUST STARTED ACTING UP SIMILARLY BUT WITH A ZERO CURRENT AS -20.4 AMP. VOLTAGES AND TIME ALL DISPLAY CORRECTLY. NEED ADVISE ON WHAT IS HAPPENING AND HOW CAN THE CURRENT CAN BE ZEROED OUT.