Have you ever made a bid based on the assumption that your partner has forgotten your system? It’s not as unreasonable as it might sound. Everyone forgets bits of their system now and again, and if a bid doesn’t make sense to you, that could well be why. Even so, it’s an uncomfortable dilemma: whether to assume your partner has erred and risk a very red face if they haven’t, or trust them at the risk of landing in a ridiculous contract.