I checked your install manual. I would recommend you go into the setup menu and go to option 3 to turn OFF adaptive intelligent recovery mode. Especially on a new thermostat this setting will turn off and on your system trying to anticipate how long it will take to get to and maintain the set temp. It's nice in a home setting however in an RV I think I would leave it off. Try that. Is this thermostat being used for heat only?
2014 Windjammer 3025W Diamond 34.5 ft 8300 lbs.
2010 F150 SC XLT 4x4 5.4L, 3.55 gears 20" rims
12 k Equalizer WDH, Firestone Airbags, HD Bilsteins
TST 507RV TPMS