AC Pressure Readings Fluctuations What Do They Mean?

My 2015 Chrysler Town & Country ac has been gradually getting warmer until recently it completely went out and only blows warm to luke warm air. I do not see any visible leaks and there are no strange sounds or smells coming from the system. When I turn the ac on the compressor clutch kicks on and visually it seems that it’s working fine. The high pressure lines are hot to the touch and the low pressure is not cold, but is colder than the surrounding engine compartment. I hooked up the pressure gauges to the high and low side and got the following reading.

It was 72-75 degrees outside when I tested.

With the car off the readings were 90 psi on the high and low side. With car on and the ac off the readings were the same. When I turn the ac on the low drops to about 20 psi and the high goes to 100psi. It will stay at that pressure for a few seconds and then gradually rises up to 40 psi on the low side and up to 210 on the high side. It then gradually drops back down to 20-22 psi low and 100-105 psi on the high side. It will continue fluctuating up to 40-42 low and 210-215 on the high side and down to 20-22 low and 100-105 high. I had I running for about 20 minutes and this just kept happening consistently.

I’m afraid to add more r134a due to the high side readings. Any ideas on what the issue might be?

Are cooling fans running?

They are running.