There are all sorts of possibilities - in the past I've had trouble with motivation when my employer has insisted on doing things in a stupid way for no reason,

There are all sorts of possibilities - in the past I've had trouble with motivation when my employer has insisted on doing things in a stupid way for no reason, or when their development methodology boils down to "I don't know what I want... but that's not it! work harder!" Bottom line is that your dev isn't happy. Why isn't he happy? That's for you and him to find out - and be prepared for it to be your fault.