I'm banging my head against the same issue years later! Preparation is spelt correctly in my coding keys but when I print the value of 'data' I'm getting: Optional("{"preparation_time":20}") I don't know if the additional symbols and punctuation are an issue or not.

Found it! All due to a simple spelling mistake in the OrderRespone model - 'CondingKeys' instead of 'CodingKeys' I feel so stupid!