Guy Miner,
I can't really help on the powder measure... I have one, but haven't used it in years... An initial thought is that a part has worn-out or more specifically developed some play. I think the drum or volume adjustment can require replacement. I very well could be wrong, but an email or phone call to RCBS might be worth your time.
Historically the RCBS 1500 has been considered the cream of the crop when it comes to electronic dispensers -
http://www.accurateshooter.com/gear-rev ... -part-one/ and
http://www.accurateshooter.com/gear-rev ... -part-two/.
Like many electric devices, my RCBS 1500 has some issues due to static build-up, temp (does not like below 65-67 degrees F) and humidity. Mine looks to generally runs lighter than my target weight by 0.1-0.2 grains - this is a calibration / check scale issue. Usually 55.4 grains of IMR 4831 on my M5 scale or Gempro 250 will display as 55.2-55.3 grains on the RCBS 1500. On a good day with powder it likes it will stay within 0.05 grains plus or minus of the target weight. On a really bad day with powder it doesn't like, it will over charge by 0.5 grains. It lets me know on 0.1+ grain overcharges via a beep and a visual indicator. A reducer nozzle / McDonalds straw helps with overcharges but it isn't a cure all. It is pretty easy to clean and change powders. It is fairly quick at dispensing and instructions on how to change the programing to adjust the dispensing motor speeds is online.
The Hornady dispenser and RCBS Lite can be good or bad; a lot depends on the individual unit and your environmental conditions.
The RCBS Lite was marketed as being better suited for the average re-loader than the RCBS 1500 when I talked to Doug at RCBS. The main differences were that the 1500 is designed with a higher weight limit to accommodate 50 bmg rounds and other heavy hitters. The Lite has a mono body, and the 1500 uses separate dispensing and weighing units. The separate bodies on the 1500 can get out of alignment and or pinch causing the weighing unit to read incorrectly.
Hope that helps.