40kW is too low for the batt degradation reduction. I would suspect cold weather but only if it was during the initial part of the charge. The X and S use electric louvers and we had one fail closed on our S which caused the charge rate to be slow and the AC couldn’t cool the cabin. There were no warning messages and it took a service appt to figure it out. Maybe that is the issue. Easy enough to see if the louvers are open during charging.
This is the battery heater could have failed.