Advice on setting up an ESP Doorbell in OH2

Don’t change it if its working.

The error may be because you are using the embeded broker but it looks like its working now.

frontdoorbell changed from OFF to ON

This should trigger the rule

rule "Play sound when someone rings Front Door Bell"
when
    Item frontdoorbell received command ON
then
    logInfo("Door", "The Ding Dong Rule worked")
    playSound("doorbell.mp3")
end

I think maybe something is not quite happy. Maybe the SD card I not sure
Do a Backup of your system.

I would clear the openHAB cache

in SSH

sudo systemctl stop openhab2.service

sudo openhab-cli clean-cache

sudo systemctl start openhab2.service 

Wait a while 

sudo systemctl restart openhab2.service