When my watch was new (early Feb '16) I would occasionally inadvertently turn my watch off at night, thus I would have no sleep data. I figured out that I could lock the device and since then it's worked great. That was my bad.
However, 3 of the last 4 nights I have no sleep data - device was locked. What could be the cause for this? I did have a pretty restless sleep last night (tossed/turned a fair bit). I do have my sleep times properly set. I also checked my 4 hour HR graph when I got up and it looked good. Could it be that it thought I was awake due to too much movement?
Max