After I power-cycle my LYWSD03MMC's, they start broadcasting with what I think is a randomised bindkey, not the one I had configured it with. The bindkey appears to be stored in flash OK, and works if I re-configure the bindkey, but stops working after a power-cycle.

Steps to reproduce:

• Configure LYWSD03MMC with:

  • advertising format: BTHome
  • adv flags: on
  • encrypted: on

• Send a bind key to the device

  • it reports it written and read OK (so looks like the flash write is good).

• disconnect

  • homeassitant then starts receiving encrypted advertisements, and homeassistant's bthome integration decrypts them OK.

• Remove the battery from the device for several seconds, then reinstall battery.

  • advertisements are still encrypted but homeassistant cannot decrypt them with the previously working bindkey.

• Connect to the device

  • "read bindkey" shows correct, original bindkey.
  • "write bindkey"
  • disconnect

• Device sends encrypted advertisements, and homeassistant can decrypt them OK.

(note: currently Homeassistant's BTHome integration has a bug where it gets stuck trying to re-auth/reconfigure the device, I'll link to the PR to fix that once I've raised it)

Guesses :-)

I notice that init_ble is called before bindkey_init but I don't know if that matters at all.

Since I can read the bindkey after a reboot it looks like the flash is working OK, but for some reason the device starts up not using the bindkey that is stored in flash.