LR4 A/C no longer maintains cabin temp on manual

I have owned my 2013 LR4 since 2016. Since then, I mostly use the air-conditioning in the following manner: manual fan speed, similar temperature settings for driver and passenger, recirculate off. During the summer months, I turn the driver temperature control to "Lo" and the cabin cools quickly. When it is too cold in the cabin, I turn the driver temperature up to 72 for example. I have an aftermarket air temperature gauge in the passenger side 12v outlet in the center console. In the past, the cabin would get to 77 degrees and I would feel the air conditioning supply cold air again and bring the cabin back down to 72. Worked well for 3 years.

Recently, I do the same procedure as above, only once I turn the driver temperature from "Lo" to 72, the air conditioning never supplies cold again. I once let the cabin get to 95 inside and only ambient air comes out of the vents, not cold air as previously. However, if I turn the driver temperature from 72 to 70, then the air turns cold again. So the cabin can get cold, but I am guessing a senor or controller has failed and won't allow the temperature to be maintained.

The vehicle is at the dealership and of course the tech says operates as designed.

Anyone have any similar issues or any ideas what could cause this problem?

Thanks in advance for any insights!