Thread / Matter Device is not sure, if it wants to be available

Hi guys!

I have a huge issue…:

I do have a Thread device, connected to my Apple Home. From there I shared the (Matter-) device to HomeAssistant.
Means for me: HA is not talking to this device via Threat, but only (!) via IPv6 over the local network.

Device ← Matter over Thread → Apple Home ← Matter over IPv6 → HomeAssistant (Matterintegration)

The issue: this device is a Smartlock btw - the device is about half the time available and the other half time not. So about 1-2 times it goes “unavailable” in HA, coming back, going again to unavailable. Every time for several hours. Periods are random…

I don’t get the point here: When the device is available, I can controll it, all good - but 1 hour later, it isn’t there anymore, sending commands to the nirvana then - another 6 hours later, the device is back available.
That means: in general it is working, communication is good and working, then again it is not working.
Where can I have a look?

I use HomeAssistant OS in a Proxmox VM, where I use 2 NICs:

NIC1.: Using IPv4 only in my VLAN3 - here are all the Shellys and IoT Stuff
NIC2.: Using IPv6 only in my VLAN6 - here is Apple Home (HomePods etc.)

→ If I activate IPv4 on NIC2, HA switches over to this as default connection (allthough NIC2 is manually set to be default) after a few days (results in some integration stop working)

Which logs can I check to get down to my issue here on Matter?

Thanks in advance!!

What Thread Border Router are you using and are you using multiple? Is the device available again if you restart the border router?

Border Routers (2 HomePod Mini and 1 Apple TV 4K) are setup as one Network (Apple Home), and the Lock is ALWAYS available in Apple Home, but sometimes not in HA - so I guess, the issue is not Thread, but Matter (from Apple Home to HA)

This is not entirely correct: Yes, HA is talking using IPv6 with the device, but the IPv6 packets are transported over Thread as well. The Apple Home Matter server is irrelevant after the device has been setup in HA: HA communicates “directly” with the device (as in destination address is the device, the Apple Home Matter server is no longer involved at that point). The only thing Apple provides here is the so called Thread Border Router, which essentially routes IPv6 packets from the LAN to the 802.15.4 RF network (Thread).

So more like:

Device ← Matter over IPv6 via Thread → Apple Thread Border Router ← Matter over IPv6 via Ethernet/WiFi → HomeAssistant (Matter Server).

This sounds an awful lot like this issue: Matter over Thread Devices unavailable - Home Assistant Only · Issue #123835 · home-assistant/core · GitHub.

Can you try removing the HomePod’s temporarily (for a day or so) and see if that improves reliability? Then add one, then the second, to see if one of the two are introducing the issues in particular.

Does your provider has IPv6 support (as in, do your devices have IPv6 global addresses assigned in your network)?

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