DBR
Thats an easy fix, you say you have a A model, so you just need to program pump on remote control to run during desired times. Also if you program remote to operate pump on flow, you can have hot water at a trickle. A shame your installer cant read the manual or attend a class to learn this.
Meli 1932
Call Navien direct and ask the tech dept, I'm sure its a bad install though
IMKTC1
You also should call Navien direct, sometimes installers and wholesale counters aren't that bright.
Having worked for a few gas equipment manufacturers in my life, a threat of lawsuit or litigation typically turns to mediation, allowing a inspection of the install by the manufacturer and another expert which 90% of the time or more turns out to be installer error or improper install including code violations. I wouldn't give up and ask for a visit from the manufacturer rep and a Navien authorized service agent.