I just installed a brand-new Zooz ZEN74 S2 800LR in-wall toggle-style dimmer switch and paired it (with S2 enabled) successfully to my C7 running latest 2.4.3.137. Wiring is correct (including neutral and ground), the 4 bulbs are a dimmable 120V 4000K type fresh from Amazon, the correct native driver for the ZEN74 got assigned, parameters all look nominal (see), and connectivity/control by Hubitat checks out great.
However... every time I turn the switch on - manually or remotely - the bulbs will momentarily blink off-on one time in perfect unison upon reaching 99%. This will be such a hit to WAF that I'm tempted to swap out the bulbs, just don't have any handy at the moment.
So I hopped on the Forum to see if any similar issues arose in the past, but only found reference to things like flickering bulbs or ones that never turn off, etc. My lights ramp up from 0% just fine, all the way to full brightness, and then it's like someone is playing a prank by quickly turning the lights off then on again.
Has anyone witnessed this behavior and have a suggestion of what to try next? Re-pair? Disable S2? Update firmware (currently reporting as 2.20, mfr. has OTA 2.40 listed as latest)? I'm of the strong belief it's gonna turn out to be the bulbs and have nothing to do with this Zooz switch, much less Hubitat. But had to ask.
Updating the firmware to 2.40 seems to have solved the "blink" problem. Although, in all fairness, I also had to exclude and re-include the ZEN74 in the process so as to remove S2 security (so the Device Firmware Update app could send data properly). So I guess we'll never know for sure...
Nope, the problem continues. I've narrowed it down to the following scenarios:
Dimming to full brightness (any target from 95% to 99%) causes two of the four bulbs to "popcorn" (bounce off then back on and stay on);
Dimming between 85% and 90% (via Hubitat, not manually) results in those same two bulbs going off and staying off (well, unlit);
Dimming switch back to full brightness returns them all to a lit state.
Think we can conclude this is neither a Hubitat nor Zooz issue, more like a manufacturing defect in the bulbs that make some of this batch unhappy with the type of dimming circuitry being used.
Oh well, shipping the whole set back to Amazon pronto. I now return you to your regular programming....
Update: I did swap the bulbs back to original dimmable LED, and while I occasionally notice a "blink", it's nothing as obvious as the fleeting "off-on" effect at/near full brightness mentioned in OP.
So, yeah, I do suspect the ZEN74 (i.e. its dimming circuitry), but now believe some dimmable LEDs are less susceptible. Maybe you get what you pay for, since I tend to be a cheapskate!
This doesn't sound like normal behavior so it could be either related to the driver in the bulbs (LED's are still all over the place and it's a race to the bottom) or something in the installation too. Our tech support team would need to see the wiring details, etc to tell what is going on but it's not common enough for us to tie it to a particular brand or model unfortunately.
