and 50s, so it should not have been. The house was maintaining heat nicely. I just saw the thermostat was always on AH. I checked as much stuff as I could. Similar to you. I also noticed my lights would flicker fairly frequently. I have an older home and usually see a slight flicker when the outside unit kicks in. But now I noted it consistently. While the unit was already running.

Called my HVAC guy. He comes out, says this is tough to figure out. Everything seemed fine. He was leaning towards some sort of issue with ducts in crawlspace drawing in cool air from crawlspace cause their 20 years old.

Finally told him about lights flickering and said I remember 6-7 years ago I had similar issue with capacitor. We go outside to unit. Sure enough capacitor dead as doorknob. The flickering was the system trying to kick the compressor on.

Anyway, he had capacitor on his truck. 5 minutes later, everything working fine.