These are very sensitive devices and certain outside forces can affect them. Make sure your area is free from drafts, heat or air ducts. Cell phones, loud music and computers can cause erratic behavior. These units should not be on the same bench as your press or other mechanical devices that can jar, rattle of shack the bench.
Have you tried dumping a charge and double checking it on your balance beam scale? BTW, whats a "Small Bucket"?