Significantly low nighttime glucose can be caused by multiple factors; a glucose spike and then reactive crash, inadequate food the day prior, or drinking alcohol just prior to bedtime.
If you sleep on your biosensor, this physical pressure can also affect your biosensor's ability to gather data and continued compression can result in falsely low glucose values that can persist for hours. Try adjusting your sleeping position to avoid sleeping on the biosensor.
To improve glucose steadiness overnight, try lifestyle changes; increased physical activity, improved nutrition choices, and healthy habits to lessen stress and promote restful sleep.