First step is to buy small thermometers and hang them at the vents to determine the temperature of each ac unit blowing cold.
You then have proof of actual temps coming out and can compare them to what is known by others. Probably get them cheap at any Walmart or similar store.
If they are blowing ice cold for sustained cycling during the heat of the day, then you have to seek other causes of cold air escaping somehow.
I will share my experience last summer with my 37ft, 2015, triple slide Silverback. Dual air, factory installed. Mine was not keeping up. Had it professionally checked. Talked directly to Dometic, NADA!! Then I called a local former dealer in my area who runs a mobile repair unit. He stopped by and checked me out and said all was fine. What I did not realize is that I did NOT have the fan on automatic AND I learned, quickly, these are NOT home units. As suggested, I start mine EARLY in the day, they run and cycle off. I drop about 3 degrees and run till cycle off. Drop 3 and on as needed. By midday, unit is COOL and stays cool with one ac running in the living room area.
I am in N Florida for 3 weeks and humidity is like 200% and avg highs are above 90 degrees daily. No issues on this trip. It may be a PITA to operate this way, but for me, it works.
I am just say'n! You may have tried same or have no luck at all. Just sharing real experience with a new unit in hot, muggy, climate.
Start with a temp gauge so you can speak in repair language to techs.
Maybe they start cold, you check and say GREAT, 2 hours later, blowing COOL VERSUS COLD. This is all happening as heat outdoors increases.
PS: we have a pure bred Maine Coon cat, 3 years old. We would NEVER leave her if we had your present concern. I am looking for a temperature alert system with I phone linkage that will notify me of excessive temperatures. Precautionary. Chances of both ac units going down are close to zero!
I feel your anxiety and frustration!