This observation may be purely anecdotal. But after a power failure in my home, many, if not most, of my devices will not work the first time. Example : My garage lights are triggered by a door switch. After a power failure, they do not work the first time, and possibly more. I have not checked. But, after the power is restored, if I activate the lights with the light Hubitat switch, on and off, then the expected automation with the door switch works the first time. Thoughts?
I would place my hub on some sort of UPS. Without details, it could be the the networks not rebuilding. I did that as a precaution prior to going to a whole-house backup (and solar panels).
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I have long considered a UPS. I just have not pulled the trigger. Our power outages are so rare here that I can justify that misstep.
How many times has this happened?
Reboot with the rebuild database option selected.
This happens every time the power to my house goes out. Maybe once every couple of months.
Certainly I could do this. But my hub has just rebooted after the power failure. And it only happens to “several” switches once, and then back to normal automation. It’s more of an observation than a nuisance.
I have similar experiences, even with LR devices and UPS. Not a bad idea to go around, from the comfort of the dashboard, to make sure everything works.
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Tempted to write a piston to “cycle” devices after a power failure.
Yeah, but I recall having to actually walk by motion sensors to get them back on track.
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Did your lights change state while the hub was off? For example, were they on, but then they default to off on power restore? The hub won't know about anything that happened when it was powered down. So, let's say this was the case: they were on, got turned off (when the hub was down -- not just for the outage itself, of course, but immediately when power was restored), then some time later, you turn them on again and expect them to trigger an automation. They likely won't, as this isn't a state change as far as the hub is concerned, and that is generally what drives events that "trigger" automations.
Specific behavior can vary a bit by device, driver, etc., but this is a general possibility. Only you can really tell more by digging into the event history for your device with knowledge of your specific automations and what event subscriptions they depend on.
One way to avoid some of this is placing the hub on a UPS, as I see also suggested above. That won't do much for mains powered devices that have this behavior (my guess above; again something you'd need to look into on your side), but if you couple that with some device that can detect power loss (the Zooz ZSE50 or ZAC38, Ring Extender 2nd Gen, probably some thermostats, homemade solutions with a realy- or contact-sensor-type device, etc.), you might be able do something after the power comes back up -- say, "Refresh" the device a few minutes later, assuming it knows and reports its actual state after power loss with such a command (again something you'd need to verify for your particular devices), set it to some specific state (if the device itself can't do this; many Z-Wave ones have a built-in parameter for power loss behavior themselves), or something else that would avoid whatever is causing your problem.
Network issues are certainly a possibility, too. You can also test that by trying to control the specific devices manually from your hub and see what happens.
Basically, don't go too far down any one path without testing to see what's the most likely problem and solution. Or, I suppose, just deal with things if it's rare enough and doesn't really bother you, also something only you can tell. 
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Interesting. I’d consider that to be pretty frequent but I guess it’s all relative. The power lines are underground where I live, so power outages only occur during truly rare, widespread blackout-type situations. Like once every decade or two.
Adding a UPS may not be a bulletproof solution but it could at least mitigate the effects of sudden power loss on your hub.
You’ll never really know if that’s a root cause until you take it out of the equation.
A UPS for the hub might help, but you also have to consider the switches and bulbs will be affected by the outage, unless you have a generator and a transfer switch. To narrow the issue down, can you cut the breaker to one of the affected switches and see what happens? I have all my hubs on a PiPower UPS, and with power blips I have some lights that behave badly
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Yeah, a UPS is certainly a good thing, to avoid DB corruption issues, and then even more problems - But I've seen similiar sorts of issues with field devices and my hubs and network gear are all on UPSs - The wired switches and smart bulbs are obviously not, and they go down while the battery based sensors are obviously not impacted.
My sense is that when main powered field devices reboot, or power cycle - They loose persistant connections to the hub for subscriptions and status reports, I also believe the hub will eventually reconnect given various refresh and status check jobs (within a few hours.. - I just have anecdotal evidence here). And on a immediate reboot of devices and the hub (not on a UPS), it becomes a race condition as to which end is up 1st. So once things stabilize after an outage (5-10 mins), where a hub went down, my best suggestion is to do one more controlled hub reboot to re-establish all the call backs and subscriptons, and if the hub went down ungracefully, its a really, really good idea to rebuild the DB anyways (or you WILL have problems down the road eventually).
Even with a UPS, I often do a manual reboot of the communication hub (ZW/ZB/Matter) just to get all the connections re-established with a bit more expediency - If I'm not home or it's a outage while I'm sleeping, things usually sort themselves out within a hour or so (again, just personal experience)
That has been my experience.
I noticed this issue of my hubitat not working ‘right’ after a power outage, especially with some of my integrations.
If something isn’t “right” after your power is restored, I think it’s unlikely there’s a single, underlying issue at play.
If you have more information to share, it’s possible there’s something more specific to point to in your case.
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I have a similar issue with my smart bulbs. I have my hubs on UPSs. I have written a rule that monitors the power of the ring range extender to monitor when power goes out. When it goes back to main I have it wait a period of time then cycle all smart bulbs to put everything back into sequence. It works well for the issues I have encountered.
This. Database corruption or electrical damage that the hub cannot recover from. A small inexpensive ups for the hub would cost less than a couple of switches. Way less than the inconvenience of setting up things from scratch again.
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My Ring Integration is the main thing that fails whenever i have a power blip, even though it says my connection is still there. The reboot with database rebuild fixed it. All good now.