High Altitude AC use causing Onan generator to die

I recently had my generator properly adjusted by a certified Onan tech. It starts and ran fantastically up to 5,000 ft. When I went up to 7,500 feet, the air conditioner wouldn't start and the generator would immediately die. Also, the microwave failed to start with the generator dying. The altitude adjustment was turned to the highest level and the generator showed trouble code 36. It was also 85-90 degrees at 7,500 feet. Everything worked fine once we left the high altitude. We have an upcoming trip to the Grand Canyon south rim which is 7,000 and may also be warm.
In reading online, I see that there is a drop of 3% per 1,000 feet rise above sea level and generator capacity drops along with some for heat. This was probably the reason for the generator dying upon start up of appliances because of spiking amperage. I tried flipping all the circuits off except those needed for the generator and the appliance, but it still failed to start.
Question, would a soft start installed on the roof AC correct the issue or will it still cause the generator to die? Microwave isn't an issue as I can run it off thge 2000 watt inverter I have.