It’s so weird that the calibration works for me during the activity. I have to be on the navigation screen for it to work. Maybe that clue was missing… Anyways, I can still hardly believe this sloppy engineering work: a watch that is not able to really store/save the calibration with a magnetic charging connector

@jmoneygrip I agree. I also found that the OHR is fairly accurate during activity. It is reasonably close ( at least during trail runs) to what I record on my chest HR monitor. I am satisfied from that standpoint. What annoys me are all the huge spikes in HR readings at rest and during the night. I do not probably meet the characteristics of the perfect target customer for the S9P; hence, I may care about wellness data from the watch ( and HR reading outside an activity or training) more than the average customer. However I still think this is an issue as these readings may affect sleeping scores and other metrics.