I recently installed my Ai system at a friends shop. Virgin Linux install. Everything was working fine except the node-red flow that does the Email notifications and dashboard controller to set the operating mode.
Turns out there is a "new" property on the MQTT input node to select string or buffer output. Half of the mqtt input nodes from my import-->clipboard installation ended up with the wrong setting. My 19.5 node-red systems don't have this property. I believe his system ended up with 20.5
Its just something I need to be aware of going forward and, maybe a useful heads up to someone who might encounter this after an update or when like me, moving a flow to a new installation.