Depends on the bulb but I assume these bulbs are not repeaters. The Sengleds I have are not.
I have a group of Segleds, although not in the same fixture all get turned on and off by the same switch. Its 4 bulbs on my front porch. I have them hardwired, so all control is though HE. When I lose power, however, they all go off and then when power is restored just come on and stay on, along with a few other bulbs I use in my pantry and closets though out the house, until a rule takes over and turns them off.
During the day this can mean they can stay on several hours before they get turned off again. I recently added a ring extender that lets me know if there has been a power outage. Now on a power restore all the bulbs get turned off.
You are sure you have no rule setup that is turning them off? I would look on the device page and see if any rules are attached to the bulbs.
It seems like I have heard that maybe some versions of the bulbs behave differently to power outages than others, so perhaps it is a bulb issue, but since you say they stay on when not connected to the hub, then something from HE must be telling it to turn them off.
If i recall correctly, the sengled drivers were intentionally changed a few releases ago to have this (often unexpected) behavior with power loss/restore.
@bravenel Not true. I had them wired in this way with my previous Smartthings hub, and had no issue. This is indicates a race condition in the Hubitat Hub is switching them off.
@terminal3 These work fine as long as they are in separate fixtures. The race condition appears when they are in the same fixture.
Here is another thread on the subject.
The recommendation is to use the legacy drivers for this use case.
@mike.maxwell or @bravenel may have more details on this behavior, but my understanding is that it is related to inconsistent messages from the bulbs when they lose power.
Smart bulbs should not be controlled with a light switch, otherwise why get a smart bulb in the first place.
If you insist on doing this with the sengled bulbs use the legacy versions as they dont have the power restore to last state feature.
It is true, just because you didn't see this behaviour before doesn't mean it's the correct way to use these lamps. Your notice that ZigBee lamps have a smaller maximum switch cycle compared to normal none smart lamps. The reason being they are not designed to be powered on and off.
Cree are repeaters (bad ones) they will cause even more issues dropping the power to them.
Most ZigBee lamps will power to on after a power cycle, very few (unless connected to there own manufacturers hub) record the last state.
Hubitat did a work around in the driver for most good lamps, that now when they power up they report and the hub can tell them what state to go too.
I don't really see the difference. Each fixture on my porch is powered from the same line. So basically it is a single fixture, it's just the bulbs are not close together. I guess you are saying it's the proximity to each other? I don't really see how that could effect them, unless it's some type of interference in the ZigBee signal.
None the less, what most others have said here is good advice these bulbs are not meant to be used by turning them on and off manually.
You left ST for a reason, as did I. There are some things maybe that worked better, in my case my Z-wave locks worked better on ST, but I have gotten them fairly stable on HE. That one issue though is far outweighed, for me anyway, by other HE features.
@user2442 You seem to have two basic issues. Sengled bulbs don't repeat. Get some repeaters in your mesh close by. Secondly you are cutting mains power to the bulbs. Zigbee/z-wave devices are not designed for this. You should be using a smart switch Like Inovelli or Zooz that has a smart bulb capability. What this allows is for the bulbs to always be connected to the mains so that the mesh is aware of them and they are on to accept command but the switch itself is transparently normal (because it's now essentially a button controller).
