I just did a search for Apple Watch and found this Tread...
I just did firmware upgrade - IMU calibration - went outside as usual to recalibrate the compass in the same spot as always - nothing around as noted at all. Calibration failed 3 times - UGH!!! WTF!!!
Then I realized, I was wearing my Apple Watch ??? Could it be that? Sure enough - as soon as I took it off all calibrated fine. I guess I never had it on all the other times I have recalibrated the compass.
I don't think I will even fly again while wearing it.
I wonder what it is doing to my wrist etc... LOL!