I am almost retired from making candles and tarts. Have Prest pots, Turkey fryer, plastic pitchers to mix in for over 100 scents, smaller plastic cups to pour with and a microwave. Been at this since 1999. I have used a microwave to remelt in for most of those years. It doesn't work with paraffin unless it's mixed with soy. Any way, about your scale. Mine has done that before when it need new batteries and when it was going bad. I'm sure you would have noticed it before since we are checking the amount we are adding. Your just second guessing. Put new batteries in and see how it does. The last scale I bought had a plug so I didn't have to mess with batteries. Love it. Good luck, it's not easy and can change with every order you make.