I am having similar issues with the A/C on my 2015 (V6 with manual A/C). Will put out 40 degree air at the vents for a while when first starting out, then the air at the vents will climb to 60-70 degrees. Frequently after driving for 30 minutes or so. It will stay at 60-70 degrees for upwards of 20 minutes, then go back to 40 degrees gradually. The air temperature also goes up to 50-60 when sitting at stop lights, and never goes below 50 when just idling.
The system drains just fine, so I know the drain isn't blocked. No clicking from door actuators. The pressure on the low side port this afternoon was 40psi when the ambient temperature was 92F. That seems slightly low to me. I think it should be between 45-50psi. I am thinking about putting some refrigerant in the system to bring the low side pressure up a little to see if that makes a difference.