random.sample producing same output when iterated over inside function

I'm trying to write a poker hand evaluator with a monte carlo simulation.

When simulating game outcomes (e.g. dealing cards) inside a function using random.sample randomization works fine.

def simulate(hands, board):
# create deck
suits = ['d','s','c','h']
ranks = ['A','2','3','4','5','6','7','8','9','T','J','Q','K']
cards = []
for r in ranks:
    for s in suits:
        cards.append(r+s)

# shuffle deck
deck = random.sample(cards,len(cards)) 
# remove board and player cards from deck
deck = list(filter(lambda x: x not in board, deck))
for hand in hands:
      deck = list(filter(lambda x: x not in hand, deck))

# deal turn and river
while len(board) < 5:
    card = deck.pop(0)
    board.append(card)
return board

for i in range(2):
    outcome = simulate([['Ah', 'Ac'], ['7s', '6s']], ['2d', '5s', '8s'])
    print(outcome)
Output:
['2d', '5s', '8s', '9s', 'Jc']
['2d', '5s', '8s', '4s', '3s']

If I run this inside a for loop it works fine but once I put this into another function randomization fails and I keep getting the same result.

def monte_carlo(hands, board, samples=5):
    for i in range(samples):
        outcome = simulate(hands, board)
        print(outcome)

monte_carlo([['Ah', 'Ac'], ['7s', '6s']], ['2d', '5s', '8s'])

Output:
Board  ['2d', '5s', '8s', '2c', '4d']
None
Board  ['2d', '5s', '8s', '2c', '4d']
None
Board  ['2d', '5s', '8s', '2c', '4d']
None
Board  ['2d', '5s', '8s', '2c', '4d']
None
Board  ['2d', '5s', '8s', '2c', '4d']

What is the reason for this behaviour?