There are contract disputes all the time over what a word or phrase means, and what a judge will look at is which interpretation best aligns with the broad strokes of what the parties were agreeing to. Nobody agrees to a contract that contains "I get to void the entire agreement at my discretion, keep the proceeds, and leave you with nothing"
Talking about (smart) contracts in general, if both parties agree that there was an error they can resolve it without any court. The problem is when only one party disagrees.
Imagine you have a contract with the bank and agree to pay 10% interest on a loan. Later on you try to claim you just weren't paying attention and thought it's 1.0%. That's a hell of a case to prove in front of a judge. And if that were the case the concept of contract would be worthless, invalidated by simply claiming "I didn't mean that".
A smart-contract should be easily reproducible. If that piece of code consistently returns the same result under the specified conditions then it's valid even if the result was because of a mistake the author made while preparing it.