problem in Unity, this code freezes the play mode after the first moved piece, how could it be fixed?

IEnumerator ClearAndRefillBoardRoutine(List<GamePiece> gamePieces){
    m_playerInputEnabled = false;
    List<GamePiece> matches = gamePieces;

    do {
        yield return StartCoroutine(ClearAndCollapseRoutine(matches));
        yield return null;

        yield return StartCoroutine(RefillRoutine());
        matches = FindAllMatches();
        yield return new WaitForSeconds(0.5f);
    }
    while (matches.Count != 0);

    m_playerInputEnabled = true;
}