If you turn off Bluetooth on an iPhone through the Control Center interface, it doesn’t actually turn Bluetooth off. The Bluetooth and Wi-Fi controls in CC only disconnect devices from those services.

A tiny device is responsible for sending iPhones into never-ending denial-of-service (DoS) loops. As of now, the only surefire way to keep your iPhone safe is to turn off your Bluetooth connection in ...

Restart > clean connections > use a different charger > replace the cable > bring the phone closer. Check Bluetooth connection > disconnect other Bluetooth devices > restart Fitbit app > check for ...