VZM31-SN OTA Update Failing on two switches - (A - 2.08) and (B - 2.00) Won't Update to Stack 0.3 build 4

Setup:

  • Home Assistant with Zigbee2MQTT 2.10.1

  • Multiple Inovelli Blue VZM31-SN switches throughout the house

Issue: Two VZM31-SN switches won’t take the latest firmware (App: 0.1 build 2 / Stack: 0.3 build 4):

  • Foyer Light Switch, currently on firmware 2.08 (20221110), Stack: 0.2 build 8

  • Front Porch Lights, currently on firmware 2.00 (20200805), Stack: 0.2 build 0

Steps already tried:

  • Re-interview via Z2M

  • Remove and re-pair both switches

  • Power cycle via breaker

  • Power cycle via air gap

  • Restarted Z2M between attempts

  • Waited for other OTA updates to complete before retrying

  • Both have strong LQI (136 and 148) and sit right next to each other, so signal isn’t the issue

What’s happening:

Foyer: Fails quickly with “Device did not start/finish firmware download after being notified. (Delivery failed for ‘26659’)”. One exception: the last attempt ran for about 30 minutes, appeared to finish, but the update never applied. Showed available again immediately.

Front Porch: Looked like it worked. Green LED flashed through the download, showed completion, then immediately re-queued the update.

Additional context:

  • Other VZM31-SN switches in the house on newer firmware (2.11, 3.04) updated to Stack: 0.3 build 4 without any trouble

  • Both switches (and everything else) are throwing UNSUPPORTED_ATTRIBUTE configure errors in Z2M logs. Looks like the known issue in Z2M GitHub #31616, where herdsman-converters 26.46.0 tries to read attributes not present in older firmware. Probably unrelated to the OTA failure, but mentioning it for context (Inovelli Blue Can't Configure with Latest Firmware · Issue #31616 · Koenkk/zigbee2mqtt · GitHub)

  • Both switches are otherwise working fine for basic on/off

Question: Is there an intermediate firmware needed to get from Stack 0.2 build 8 (or 0.2 build 0) to Stack 0.3 build 4? If so, is there a manual OTA file to do a staged update? Is there something I’m missing on getting these two to update?

I recommend reading through this thread: VZM31-SN Firmware upgrade failures going from 2.18 to 3.04

There’s several different steps that are suggested there but if all else fails, you’ll need to do a cabled flash.