Lets straighten this up. WHY go to a Doctor or Lawyer? Just call the Receptionist. She obviously KNOWS everything the Professional does. Why bother the Professional that has the answers????????
1. Salesman are SALESMAN. Why anybody would think they repair or have knowledge of the technical aspects of RV's is ridiculous.
2. Except for VERY few cases, Service advisors and Managers of Service also have NO knowledge of technical aspects of the products. They are hired to MANAGE people and customers.
3. MOST IMPORTANT. The D-2 is the DEFAULT setting on ALL Dometic tstats. That means that someone reset the Tstat to D-1. So, while the OP found the solution to the problem, there is really NO problem. I have 38 years as a RV technician and still working as a technician. I service thousands of RV's every year. Until the OP presented his problem and solution, I had never heard of this or had a customer complain of this. WHY? Easy, NOBODY ever goes into the set up for the tstat and reprograms from D-2 to D-1. Doug