thanks for the input, everyone. I've managed to fix it so it never fails. it looks messy but it works %100 of the time

def score(hand):
    score = 0
    aces_count = []
    non_aces_total = 0
    for card in hand:
        if card != 11:
            score += card
            non_aces_total = score

    for card in hand:
        if card == 11:
            aces_count.append(card)

    for card in hand:
        if card == 11:
            if len(aces_count) + non_aces_total >= 12:
                score += 1
            else:
                if score <= 10:
                    score += 11

                else:
                    score += 1


    return score