Airflow Question

I have 2 Dometic aircon units in my rig, one for the main area and a low profile unit for the bedroom.
I have not been getting the airflow into the bedroom unit as one would expect for such a small area, so I opened up the air intake in the bedroom, cleaned the foam, resealed everything inside with aluminum tape and made certain that ther e incoming and outgoing air is connecting and leaking into each other. I also removed the 2 vents in the bedroom and cleaned them out looked for issues and found none. So next I went to the bathroom and taped the aircon vent up in there with aluminum tape as to stop the air coming in there, and hoping that the airflow into the bedroom would improve, but it did not.

Then last night while I was in the bedroom with the bedroom air off and the main air on in the living area I could feel air coming through the vents in the bedroom, just a small amount of air, but airflow. So I turned the main off and the bedroom air on and got about the same amount of air coming through in the bedroom (very low amount) and both the fan and the cooling pump in the bedroom unit are working, or sound like they are (I can hear the fan start and then the pump start a fe number of seconds after the fan.) I have switched the thermostats, and while I originally thought that the thermostat in the bedroom was broken, it turns out that it is not as it now controls the main aircon unit and works just fine, and the one that now runs the bedroom is behaving just like the swapped out unit.

With all of that as a precursor, is it possible that the vents are all connected incorrectly, or are all the vents for the front and rear all connected to the same system of pipes or are they supposed to be separate (I would expect separate), and how do I go about sorting this out, for it would be nice to have a cool bedroom and have the air turn off promptly, rather than it taking hours to cool down from 73 degrees to 72 in the bedroom.

Oh, and the low profile unit for the bedroom does not have the large vent next to it that is part of the air intake for the main unit in the living area where the bulk of the air comes through.

It seems that the more I learn about 5ers in general the more I find that needs to be repaired or sorted out. (In a weird way this is good, as I am being kept busy bothering the **** out of you guys ... ha ha ha)

Any idea and suggestions where to start debugging and sorting this out.

I'm not sure about your bighorn but on my Gateway both AC units are connected to the same vent system. If either unit is running air comes out of all vents. It does seem like more air flow comes out of the vents closest to the unit that is running but I would expect that. That being said if my bedroom unit is running a lot of air comes from the vents in the bedroom and the room cools off quickly and the unit shuts off so something isn't right with yours if the bedroom vents have low airflow and it takes a long time for the room to cool down enough to cycle off the unit.

Have you pulled the cover off and looked up into the duct system or is your bighorn one of the systems with no access panel under the A/C unit into the duct system?

I would install the bedroom AC so that it only blows out directly and does not connect to the ducts.