Crashing during sleep tracking seems very rare but still may happen on some firmwares, especially on custom ROMs.
Here is a list of featured with has been reported as causing rare crashing issues on specific firmwares. You may want to try disabling them:
– noise recording
– screen dimming
– wake up with flashlight
Also make sure you don’t use any task killer apps or automated backup tools. And if you insist on using them than please try to white-list Sleep as Android.
Also it may happen that the app updates during the night. We have a restarting mechanism in the Sleep as Android Unlock app which shall restore sleep tracking under normal conditions. If this mechanism is failing for some reason you may want to disable auto-updating or track with airplane mode which is anyway highly recommended.
Finding out what is the cause of the problem on each individual firmware is a very difficult task as this problem is not caused by the application but on the contrary by a bug in the firmware itself.
If you would like to help us debug the problem please try the following (SD card needed, Android <4.2!):
1) Download alogrec (free) from Play Store
2) Start it before you start tracking.
3) Start tracking.
4) If the tracking is not running in the morning, send us the output of alogrec.