Basically the title: Don’t upgrade firmware on your Zooz ZEN15 from 1.03 to 1.06 at risk of losing meter functions.
I did this to multiple Zen15 devices, even though the firmware download page says it’s acceptable, but I ended up losing metering on all of them that were originally on 1.03 firmware. One early symptom was updating from 1.03 to 1.06 caused them to become unresponsive after updating: the LED stayed red with the relay off, and would not respond to z-wave commands or local button to turn on the relay. They required a hard reset and re-inclusion to recover. Unfortunately after this the metering functions are invalid: they report inaccurate values and overload protection trips constantly. It feels to me like a loss of internal calibration.
This means that they’re now only usable as a switch (after disabling overload protection which now trips on the smallest loads). Unfortunately 1.03 units are older which means they’re probably out of warranty, and now they’re trash for me since I was using them with the energy dashboard.
Updating from 1.04 was fine though: all of my ZEN15 that were running 1.04 survived being updated to 1.06 (without having to be hard reset and with metering functions intact).
Edit: I did work with Zooz support and it came down to warranty age.
Edit 2: Zooz did offer me a discount on new ones… but yeah think twice about updating older ones that shipped with 1.03. Maybe ask support about updating to 1.04 first then to 1.06.