Android Devices Bluetooth Cached

There is a problem in my application: whenever I launch my application and click on a button to search for bluetooth devices (which scans for bluetooth devices from its application), my application does not always show devices in range (sometimes it shows one or more devices, and sometimes an empty list appears). This is because Bluetooth devices are getting cached and when the app starts, it doesn't find any new device. The same happens when manually scanning from the built-in variant of the Android device. I am trying to use Samsung Galaxy GT-1900 (2.2.1) and Samsum Nexus (4.0.2). Can anyone advise on this. Thank you. ,,