Matter commissioning fails (bad IPv6 address maybe?) | Home Assistant | Page 1

I'm running into some problems commissioning a Matter-over-Thread device to Home assistant.

I initially ran into the issue with Eve switch, but now using an ESP with example firmware to get more insight on the device side of things (same behavior for both).
Using Docker HA and a Docker python-matter-server.
Using the Espressif Open Thread Border Router as my border router.
Commissioning works without any problems if I use Google Home (I don't have any Google border routers, but have some 1st gen Nest Hubs / Android phone). After commissioning via Google Home, I still can't add it to Home Assistant.
The device does sucessfully join the thread network.

When trying to commission, I get the following logs on the python-matter-server:

2025-04-02 21:37:12.636 (MainThread) INFO [matter_server.server.device_controller] Starting Matter commissioning using Node ID 19 and IP fd21:879b:d565:1:7413:d3ba:e505:9eef.
2025-04-02 21:37:16.535 (Dummy-2) CHIP_ERROR [chip.native.EM] <<5 [E:5311i with Node: <0000000000000000, 0> S:0 M:225590691] (U) Msg Retransmission to 0:0000000000000000 failure (max retries:4)
2025-04-02 21:37:23.086 (Dummy-2) CHIP_ERROR [chip.native.SC] PASESession timed out while waiting for a response from the peer. Expected message type was 33
2025-04-02 21:37:23.086 (Dummy-2) CHIP_ERROR [chip.native.ZCL] Secure Pairing Failed
2025-04-02 21:37:23.086 (Dummy-2) WARNING [chip.ChipDeviceCtrl] Failed to establish secure session to device: src/controller/python/ChipDeviceController-ScriptDevicePairingDelegate.cpp:96: CHIP Error 0x00000003: Incorrect state
2025-04-02 21:37:23.087 (MainThread) ERROR [matter_server.server.client_handler] [128741987707040] Error while handling: commission_on_network: Commissioning failed for node 19.

From the PMS, I can't ping that fd21:... IPv6 address, but it also doesn't match up with the "Mesh Local Address" fd2e:... or "On-Mesh Prefix" fd11:22:: from the OpenThread Border Router configuration.

If I click the "Add" button in the Border Router Web UI under "On-Mesh Prefix" nothing really changes there but it does seem like sometimes the device will get an IPv6 starting with fd11:22..., but that IP also isn't reachable from the PMS. I briefly tried adding a static route on my router for various prefixes using the Border Router as the next hop, but that didn't seem to improve anything (just changed the error from "no route" to "unreachable").

Because commissioning works fine through Google Home, and because even via Home Assistant the device successfully joins the thread network, the issue seems to be with the communication between PMS and the device. The IP not being reachable seems related as well, but I'm not even sure why that's the IP it's trying to connect to in the first place since it doesn't seem to match anything else.

Has anyone seen a similar issue?
Does anyone know how PMS gets that IP address? I'm fairly sure it's the wrong one, but I don't know how to provide the correct one.

#Matter commissioning fails (bad IPv6 address maybe?)