When Ferry Westlake is trapped in the crypt, he finds a coffin and opens it. We never see him close it. When Spedding enters the crypt a few minutes later, he climbs over the, now closed, coffin. Another few minutes later he comes to the coffin again, which is now open.
When locked in the vault, Westlake finds a coffin and opens it. We never see him close it. A few minutes later, Spedding enters the vault and finds the coffin, which is now closed and climbs across it. Another few seconds later, Westlake has already left the vault, and Spedding again comes across the coffin, which is now open again.