What do you have plugged in that is changing in power draw so frequently, that is not normal.
As I was just looking at the parameters for the ZEN04 I realized, that I think this N4003 is just a clone of it. The ZEN04 has the same limit of 5-50 watts and same parameter number 5 for the power reporting. The original ZEN04 was spamming 0 volts a lot but they fixed it with the 1.20 firmware, is your sending 0 volts reports?
This post explains the accessory attribute and setting: [DRIVER] Zooz Smart Plugs Advanced (ZEN04 / ZEN05 / ZEN14) - #56 by jtp10181
