I have a powder pro digital scale and just recently it started “drifting” and not just a little. Sitting empty on my bench (climate controlled, no fan, wind or other outside forces) it will not zero over the span of 30 seconds it will very by as much as 3 grains. Has anyone seen this, is it worth sending in, can it be repaired. I also have the dispenser that goes with it and is mostly useless without it. Any comments would be appreciated.