It came from Amazon, so return it. I don't know why we insist on fixing defective stuff that we receive. Myself included. My wife gives me hell every time I try to make busted stuff work. Even if you've had it too long, call up customer service and see what they can do for you. Tell them that the people on Home-Shop Machinists forum feel that it is a defective unit. It doesn't matter if it is the capacitive scale, the cable, or the read out. It is defective.
Loosing zero is a common occurrence with that type of scale. You learn to live with its limitations. They sometimes loose their mind when moving fast, but random numbers while stationary or moving slow is busted. Tighten the mounts, swap the cables, but I'm thinking you need it replaced.
