One of the features of the Broadcom stack is that when you attempt to connect to a virtual COM port it will show the user the Bluetooth Manager and ask them to select a paired device to connect to. You can suppress this and have it always connect to the last used device. You’ll need to write to the registry key:-
Create a DWORD value named BTBrowserEnabled and set the value to 0. If you want to re-enable this feature you can reset the value to 1.