Just a point of comparison, I just tested mine as it stays out on the bench all of the time. It took about ~5 sec to settle at 118.7vac maybe even less, I tested multiple times. the harmonic ratio worked as expected when hooked up in the(min max avg) mode(0.0,0.0,0.0) I just tested this again and found the same thing as you, the avg reading seemed over the place, it also slowly counted down from the high value as i was looking at it (actual average 0.1) (meter reading 78.88 and slowly dropping). It appears to only happen with small min/max readings, it worked perfectly when the min was 1.0 and the max was 29.5. That being said, I don't use this function at all really, more of a novelty for me. (useful in an industrial setting)