I've had thermostat issues on my 2016 Greyhawk. My thermostat would lose the temperature setting I set whenever the furnace would try to ignite, it would always reset to the factory default temperature.
I *finally* figured it out and fixed it. The thermostat power was wired to the power wire feeding the furnace. When the furnace would light, the power would drop from 13V to 11V (or lower) and the thermostat would lose my setting and reset. I rewired the thermostat to another power feed (in my case, the power awning) and the problem went away.
The wire size Jayco decided to use to the furnace is a dedicated 14 gauge wire - bare minimum. I'm going to run a new 10 gauge wire from the furnace to the fuse panel, still using the 15 amp fuse to reduce the voltage drop.
Even plugged in to 120v shore power, 11 volts to the furnace is borderline for proper operation due to the sail switch reading air volume.
Hope this helps,