When pressing the first number in the dialer, the phone searches for any number stored as speed dial or shows possible matches.
The DTMF tone for the first digit does not stop to play until the results for the possible contacts is shown. During this time, the screen freezes and you cannot enter any other digit.
Occurrence: This does not happen everytime you dial the first digit. Rather, when the dialer is minimized (not in focus) and then brought to front to dial a number,
Probable Cause: The function to query the contacts runs in the same thread and is not asynchronous.