QBluetoothDeviceDiscoveryAgent supposedly  returns / sends signal upon bluetooth device discovery. That "discovery"  signal is generated from some unknown database filled during FIRST run of the btscanner. 

Subsequent "device detected" runs are  NOT results of physical bluetooth inquiry for nearby  devices.

Since clear( ) is NOT implemented in QBluetoothDeviceDiscoveryAgent there is no easy way to delete this phony result.

Also - these phony results will be processed  BEFORE start ( scan) ,  fished signal  will also be generated - in due time   and with NO "device detected"  generated  between  start and  and finished  signals. .