I don't have your model scale, but I'm assuming it's got knife edged vee blocks on the beam that fit into vees on the base. First, clean out the vees in the base and be sure the vee blocks on the beam are clean. Most manufacturers tell you to keep everything oil free and dry.
Static can drive a scale nuts. Lyman warns that having anything made of styrofoam near a scale will do it. Have you got one of those styrofoam cartridge blocks that Winchester uses on the bench? If so, get it off. Seen it happen.
It's getting past the static season, but if you get zapped every time you touch a light switch, get the humidity up somehow.
The knife edges may be worn or damaged. If so, send it back to RCBS for repair. They're real good on warrenty.
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