Plastic can also be made on "Monday". I want to say from my own experience, anomalies occur in the casting, injection molding of plastic. In this process, they use old ground plastic and add unused raw plastic! It is difficult for me to express...
An update to my case, in case it might be helpful to anyone.
After contacting dji support, they suggested to send the unit back to them for inspection.
Before doing so, I thought to try one more time to self-calibrate the sensors.
DJI support...
wow...that solidifies my thinking that I should use the slower charging but have not done so yet. I will leave fast charging for when I absolutely need it :). Dunno if that's the cause but it seems likely. if it was just one battery I'd think it...
Thanks for the info. I think to get into finding the cause, it might be good to pin down things like how many charge cycles do the batteries have, how low were they discharged after a flight, things like that.