Temperature cooling reads NA while cooling; not cooling

While imaging, I am setting the camera to cool. But in the course of sequence, it seems to stop cooling, and the temperature reads NA. Often is starts up again and it appears that sometimes it was actually cooling while reading NA; but other times it was not cooling. I have upgraded to a 5amp power supply. Setting to -35 (been using that successfully for years), and tried cooldown times of 0, 2min, 5min, etc.; makes no apparent difference.

Sometimes the FITs heads shows an actual temperature even if the SGPro says NA, but usually the FITs header lacks actual temp data, although it shows the setpoint.

Any thoughts?