The devices that I'm having issues with are (at least):
I'm sure there are others, but these are the 3 that really piss off my wife (hah!).
Dan
Ok usually the topology map is useless but I am glad you posted it, because it is very curious.
If I am understanding it correctly the vertical 01 nearly all blue is telling us that most devices can "see" the hub. But The horizontal 01 is telling us the hub does not "see" many of the devices.
The Z-Wave details looks pretty good. I think this problem shown on the topology is causing the issues. How to solve it I have no idea.
Maybe try running a FULL Z-Wave repair?
Going to look harder at the zwave details and then update this post.
UPDATE: Nothing really stands out in Zwave Details. You have two unplugged outlets but they are showing only 1 neighbor (themselves) so they should not be causing any damage.
After you try the full zwave repair you probably will not see changes immediately, but would be good to try that and let it sit overnight, then check the topology again.
Ahhh I see, I had never really known how to interpret this visualization. Ok yeah clearly that top line 01 seems wacked. I have done a Z-Wave Repair several times. But....you said "FULL Z-Wave Repair". Is that different, and if so, how do I invoke that super powered activity? 
Dan
You can either repair single devices or the whole thing, so sounds like you have done it before. You don't want to over-do that repair either, as it causes some strain on the mesh when it is going.
I am seeing an abnormally number of devices taking Hops as well, with the C-8 I would expect most devices to direct connect. This is probably a result of the strange topology findings, the hub is taking hops because it doesnt see the devices, so then the devices respond back on that same path with the hop.
Are you by chance using a POE splitter for power? Could you test with a regular quality power block at least 1Amp if so?
Could also try swapping the two antennas around (in case one is somehow defective), and make sure they are both vertically orientated (perpendicular to the ground).
I am using the power supply that the C8 came with, nothing fancy. Yes I've run the full Z-Wave Repair several times over the past week trying to solve this. Although I hadn't looked at the topology map before vs. after, that would have been useful. I just ran it again just to see how it changes the topology map. No change really. Top line red except for 02 and 44 blue.
The antennas are both vertical and are both tight. I will swap them to see if it makes any difference.
I would be curious to see some of the extra details from this app: [BETA] A Z-Wave Mesh Tool [C7 and 2.2.4+ Only]
It breaks down the topology on a per device level, would would help to verify I am reading the topology correctly (despite confirming via tool tips I am still not confident in myself on that thing).
You just expand the little arrow for a device and it shows all the neighbor info for both directions.
Ideally the HUB should be in both tables for the device to directly connect:
The Topology Map is not a "live" display in that it's displaying historical data and could easily be an hour behind the data shown in the ZWave Details page...
However, I'm seeing a high degree of asymmetry and would highlight nodes 1, 16 and 17
Row 1 horizontally SHOULD be symmetrical with Column 1 vertically. You've got a nearly opposite display.
Column 16 and 17 are completely empty (no blue) and yet 2D is the only blue in those rows. 18 is also asymmetric but harder to see at a glance... and so on.
A bit of asymmetry is ok because at the edge of reception, one end or the other isn't going to be equal RF sensitivity. Having lots of neighbors is mostly the solution because the hub can find a path that works in both directions and stick itself to that. Your ZWave Details page looks encouraging by comparison. It's indicating no Ghosts other than your portable outlets... however, I'd encourage you to plug them back in, even if they are Holiday lighting holdovers. There's no simple rule to know which ghost is going to cause a problem. Alternatively, remove them til this issue gets more settled.
16 and 17 are unplugged, they are just a couple Leviton plug-in modules that I haven't used in a while
Cool tool, thanks for that. Here's a snippet from one of the devices having trouble. Clearly 0x01 - Hub is not in the second column.
Same is true with another device I'm having trouble with.... 0x01 - Hub is only in the first column.
I will try to plug in 16 and 17 to see if it solves it. But I didn't have trouble on my C5 with those unplugged - to your point, yeah those are Christmas light plug-ins and I haven't used them in over a year. I can try it. Still, I'd like to understand what the heck is going on.
Full screenshot of the z-wave details. Clearly a lot of my nodes aren't communicating directly, and they should be.
Strangest topology I've ever seen as well.
I think you've done enough full Z-Wave repairs, maybe one too many? 
You've done the "shut down, pull power, wait, plug in" dance recently? If not, I'd do it and let things sit overnight and see how things look the next morning.
Are you able to add and remove Z-Wave devices from your hub? Wondering if you have normal Z-Wave functionality in general.
Having to mains repeaters like that unplugged will definitely cause mesh issues, If they are seasonal you need to exclude them not just unplug them. Plug them in. Shut down the the hub from the settings menu and unplug for a few mins and power back up. Let things settle and see how it behaves.
I have a holiday lighting plug unplugged sitting here next to me, zwave works great.
Since his unplugged devices show no neighbors what problem will it cause? No device will try to talk to them.
I had a set of 3 ZWave devices that use each other for routing that extend in a straight line from the hub to my Pool area. Two of the devices that are closest to the home are 30ft from the hub. The third one is another 40 ft away. These 3 outdoor devices have always worked well but share a single circuit. High Humidity due to days of rain causes the GFCI to trip every year. Never seen an impact to the mesh over 4 years and 3 Hubitat Hub models. I did a power cycle, which is an ultra rare event for me, and the mesh went from perfect to horrible... 2 minute response times. It took days for me to decide that those "harmless" dead ZWave devices should be restored. That fixed it. My hypothesis is that when they fall off, yearly, the hub is up, and the mesh is good. As long as that's true, their absence is invisible. But a power cycle caused those harmless devices to become critical. Light rain is due again today, and if the GFCI trips, taking out those 3 devices, I'm expecting there to be no issue, just like previous years.
However, in this Topic, advice has been given to power cycle the Hub to potentially "unjam" the radio... which might elevate those missing devices into some priority that then kills the mesh.
I have unplugged, waited and rebooted the C8, also plugged in the portable Leviton plugs. Will wait to see how the topology shifts throughout the day.
Dan
My hub has been power cycled since it has been unplugged. I am thinking it has to do with the neighbors count. If other devices still consider it a neighbor they might be trying to discover it when the hub cycles.
I have tried all suggestions to no avail. I have swapped the antennas, power cycle, plugged in two portable plugs/repeaters, upgraded to the latest…nothing changes the fact that the top horizontal line in the topology map is red.
Wondering if I have a defective unit. Would love to have a staff member help out here @support_team
Dan
Download the Hubitat app
