Welcome to the forum Gordon. We have a 2016 Fuzion 420, with 3 A/C units. If you do a search on here you will see that others have had some success taking the cover off the units, inside the camper, and checking for anything obstructing the air flow. I did this and had some increase in air flow, but not enough to matter. I finally just eliminated the flow through the duct work and now have all 3 units dumping air straight down. The center unit, zone 1, is above the loft, I put a 20" fan up there only when it's very hot outside and it keeps the camper quite cool. Also, I generally have to cool all 3 zones, so I set the thermostat at our desired temp, for all 3 zones and put all 3 on auto and leave it. Turning the A/C's off at night and waiting until the camper heats back up before turning the units back on is the kiss of death.
2013 F350 CC King Ranch
2016 Fuzion 420