Have a 2015 Coachman 575/4. Transverse bed and end bathroom. First time that I have had a van with the Truma Combi (E) Plus system and having issues on the heating side (water heating is fine). The system does not maintain heat overnight, tried both ECO and High settings but after being set at 18/20 degrees (for example) overnight the system struggles to maintain 12 degrees. During the day once the outside temp has risen the system seems to have no issue maintaining a higher temperature. Have tried switching the hot water to off overnight to see if that made a difference but it did'nt. Any suggestions as to what the issue could be?