Hi there,
Yes, I have seen these issues pop up occasionally only scanning though. seems others have had it stop unexpectedly b4 also.
BLE.end or Advertise.stop ? not sure on Bluefruit, I know ArduinoBLE does.
How is it powered? Start with that being the first look.
Are you looking at the Manufacturer.Data changing in the scans to pass the data?
maybe post up the BLE SETUP part only?
HTH
GL 
PJ 