PG value describes the power supply condition.
Which psus are you using? Sorcerer psus? Do you have better luck with other psu?
I am using Sorcerer PSUS, switching units does not have a change. The PG started going down when exhaust temps went really high, I saw over 155 on the exhaust before it stopped hashing. I am running March firmware too which is suppose to have the updated thermal protection.