NUMBER type attribute to create an alert

Is this problem limited to a NUMBER type attribute?

It would have guessed the issue is that you are running thing from the thing itself (Things[me.name]).

Adding/updating an alert is a model operation, meaning you change the definition of the thing model. This means the thing has to be stopped, changed, and then restarted. This would cause the currently executing service to be stopped and that's why you get "Thing not running". 

Without testing it, I would assume it works if you move the service to a third entity.