I bought a RCBS charge-master lite about 2 months ago and was having the same exact issue you are. My procedure was to have the scale weight the powder charge. I would take power pan with a funnel and drop the powder charge in the case. Place powder pan back on scale to drop the next charge. While the scale was measuring the next charge I would move charged case to the reloading press and seat the bullet. Placed loaded round in the ammo box and restart process with new charge waiting on the scale. This is where my problem started. The vibration cause by seating the bullet was messing up the scale. My reloading bench is stable but seating a bullet ( .308, 7mm-08, 6.5CM) was causing enough interference to mess up the scale. So I modified my procedure to allow the scale to finish weighting the charge, and sound the beep, before I caused any movement, vibration etc, on the reloading bench. My problem has since gone away. The new procedure does take longer adding quite a bit of time to the process. I have thought about another table, stand etc next to the bench to isolate the scale from the press.
Try this out and see what happens. You have my curiosity up. Hope this helps Mark in Geo-Bama.