C8 (Pro) and Xiaomi Light Sensor GZCGQ01LM

[vitaliy_kh]

I have bunch of GZCGQ01LM Xiaomi Light Sensors.
Originally all these sensors were paired with C7 HE hub but eventually migrated to C8 (not Pro).
They were working very well with C8 after a migration from C7. Today one sensor required
fresh battery and as coincidence C8 was migrated to C8 Pro (BTW, migration went very smoothly without any single problem). After battery replacement Light Sensor in question lost a connection to C8 Pro and I was not able to reconnect it back. C8 Pro was seeing this sensor as previously connected but could not complete a connection.
Actually this problem is not new with C8/C8 Pro hubs. Many Tuya Zigbee devices have this problem. I.e cannot be paired with C8 but have no problem pairing with C7.
That was my fix for the problem. I paired failed sensor with C7 and brought it back to C8 Pro via already running Hub mesh.

Now my observations:

• If Zigbee Sensor, potentially failing to pair directly with C8 somehow snicked to C8 it works just
  fine until something goes wrong.
• But after a failure it is impossible to bring it back to the same C8 (I tried all available pairing options on C8 Pro).

To my EE eyes it looks like a tiny piece of pairing process is missing or misinterpreted on C8 hubs.
Zigbee Experts - Is it any reasonable explanation for the phenomena?
Yes, I know this was already discussed thousands times but I cannot recall was it the same case.
I.e. the migrated to C8 problematic Zigbee Device worked just fine until very first failure.

[bjcowles]

@vitaliy_kh

But after a failure it is impossible to bring it back to the same C8

It has been my experience that this is the case with any hub model. These sensors just don't re-join correctly and I don't know why.

For me, the easiest way to get these back on the same hub is to use Swap App Devices to replace it with a virtual omni sensor in RM rules and other HE apps, delete it, re-pair it as a new device, and then swap it back for the placeholder virtual devices. Of course, if these sensors are used in any custom/community apps, you'll need to remember to manually add them back

[hubitrep]

@vitaliy_kh

Is it any reasonable explanation for the phenomena?

An interesting theory was shared by @Tony but I don’t think it was ever confirmed by HE staff.

C8 Zigbee mesh is a hot mess

C-8 is the only HE hub to use an SoC based on the Zigbee 3.0 protocol; while this sounds like an upgrade (there's literally no performance benefit) for the typical HE user with legacy Zigbee HA profile devices, there's a significant downside: devices that disconnect might be unable to transparently rejoin the mesh as they normally would if joined to a non Zigbee 3.0 hub. It's not disconnects that are the issue; they happen even in a properly functioning mesh for a variety of reasons: …

[vitaliy_kh]

@hubitrep

An interesting theory was shared by @Tony but I don’t think it was ever confirmed by HE staff.

Thanks for reminding me. I remember reading this (and many other related) threads regarding C8 Zigbee problem. My observation could be a case.

[vitaliy_kh]

@bjcowles

For me, the easiest way to get these back on the same hub is to use Swap App Devices to replace it with a virtual omni sensor

Just in case I tried this approach.
Still No Go.
But pairing/re-pairing with the C7 is not a problem at all.

[danabw]

I've had this experience on my C8 as well. I just migrated C8 to Pro, but only a day ago so no re-pairing or new pairings on the Pro yet, but I expect it to be the same.

I also had devices that fell off the C8 (stopped reporting/responding) and were unable to re-pair as an existing device, or as a new device after being removed. Or they would re-pair but fall off again later.

My issues were also solved by moving devices that gave me issues on the C8 to the C7. There was no brand/device consistency in terms of what worked/didn't work on the C8 - i.e., it wasn't like all of a particular device were problemmatic on the C8, but rather that some % of one device, and some % of another device, etc., would have problems on the C8, while the rest of the same devices were fine. So I'd move the troublesome devices to my C7 and over time everything settled down. The devices that had to be moved were not typically troublesome devices - we're talking SmartThings and Centralite leak sensors, Visonic contact sensors, Iris v2/v3 motion sensors.

In the end all of the Zigbee devices that ended up staying on my C8 (>90) are connected via repeaters (verified w/Xbee) and that mode has been stable model for me.