I have been using the app Sleep Watch for almost a year now to track my sleep. It syncs it's data to the Health app on iOS. Earlier this week I noticed a few days of sleep data were missing in the Health app despite being available in the Sleep Watch app on iOS, so I contacted the developer and reported it as a bug. This morning I checked again and noticed the gaps of missing data seemed larger than they did before, so I compared it to the screenshot of the Health app I included in my email to the developer - and I've noticed days which had sleep data recorded in Health earlier this week are now blank. I then switched to month view and scrolled back in time, and there are *huge* chunks of time which no longer have sleep data recorded for them in the health app. I know I have worn my Watch to sleep every night - so 100% of days should have sleep data recorded. Before using Sleep Watch on my Apple Watch I was using Sleep Cycle on my iPhone to track my sleep. I made the switch on May 1 2018 according to the data which remains in the Health app (the first data recorded by Sleep Watch was recorded on May 1). All of my sleep data prior to May 1 2018 is still available in the Health app. This leads me to think there is some kind of bug or flaw with the Sleep Watch app which is potentially deleting it's data from the Health app without warning or reason. This is not simply a case of data not syncing to the Health app, because I know at least 1 day which previously had sleep data recorded in the Health app no longer does. I've reported this to the developer as well but in case anybody else out there also uses this app - I'd suggest you check your sleep data in the Health app, and be aware it may not be as accurate or comprehensive as you would expect. I won't be using this app any longer, so I guess it's time I finally download AutoSleep?