Check the ducting for crimps or longer than necessary
While installing an accumulator (for the plumbing) in our 2015 23' FB Flying Cloud I discovered heat ducts that had been smashed partially closed or longer than necessary which reduced the efficiency of moving heated air around the trailer.
Setting the thermostat is a challenge as the delta (temperature swing from on to off) is as much as 6 or 7 degrees and the location of the thermostat isn't ideal. Not much you can do with those two issues without investing more $$.
Try cracking a window or vent remote from the thermostat or remote from the area that you spend the most amount of time. It is important to allow hot air to push the cold air out of the trailer and remember hot air rises. A small battery powered fan might improve the heat distribution.
with pups Ella (the miniature poodle)
and Tibet (the Lhasa Apso)
2015 23' FB Flying Cloud
2016 Chev Silverado LT Crew