I just tried to do a flight from Manchester Airport to Mytilene Airport on the Island of Lesbos, Greece. Shortly after departing Manchester, whilst cruising on autopilot at 33000 ft, the aircraft hit turbulence. Instead of continuing to fly level, the aircraft began bobbing it’s nose up and down, becoming more severe each time. Eventually the aircraft stallled, and the autopilot disengaged, sending the aircraft into a steep dive. Had I not been near my tablet to recover from this, I would have crashed, receiving multiple overspeed violations in the process. I don’t know if this is a known issue, but it probably could have quite easily occurred later in the flight, and I would not have been able to recover. As with all my flights, I recorded the event, and despite being on timelapse mode, it shows what happened better than I can describe. I haven’t uploaded to YouTube yet, but I will. This isn’t likely to be a device issue, I restarted it before flight, and cleared all background apps. My device is a Samsung Galaxy Tab S3, running Android 7.0. If you need more info please ask and I will do my best to provide it.