The sleep score graphs on my Forerunner 955 mysteriously have a 'hole' for one of the nights. The sleep score for that night did show during the day immediately after, and it's logged and visible on the Connect App, but the next day the watch itself seems to have forgotten it. It's unclear if this affects the Training Readyness metric, given that it's based on recent sleep scores.
I just had this happen to me. Even stranger, not only did it erase my sleep record from yesterday, but it also replaced my sleep score from last night with low score for hours I wasn't even sleeping.
So here it's showing yesterday's data missing even though the GC website shows there was a record there before:
This is the sleep duration it's currently displaying for today even though that's not what appeared this morning during Morning Report:
I wasn't asleep during those hours. My sleep hours are 9pm-5am and today after the morning report, I edited my awake time to 6:40am because I slept in (it was displaying 4:42am). Current sleep score is 36/100 but it was about 60 this morning. These screenshots show the scores in Training Readiness (before) and Sleep Score (after) contradicting each other:
The watch seems to have some sort of record internally of both my legit sleep data and the bugged one because it's adding the total time in the Sleep Stages graph (also notice that the watch displays my sleep from yesterday which is disappeared):
