I have a Vetta bike computer - RT880L is the model number, I think. (It's a wireless unit.)

When I'm done with a ride the computer frequently registers speed - as if I'm riding. The bike isn't moving at all. I hang my bike and it sometimes registers speed when the bike is hung. Tonight I took the computer off the mount, walked 10-15 ft. away from the bike, and the computer was registering speed.

Is this an inherent issue with wireless computers? Or might this be a problem with this particular model? The only real issue is I can't trust the odometer.