If anyone has any sort of older device using GPS (including some older drones, but obviously not Tello) you may want to make sure it is up to date with it’s firmware before 6 April as this is the date the GPS system resets it’s ‘week’ clock back to zero. This happens every 1024 weeks - the last time being 21 August 1999. Those of you of a certain age will remember the ‘Millennium Bug’. It’s the same sort of thing. Old GPS-based devices may start having problems on 6 April 2019!