I put "I pay with my parents' credit card" and it said "Almost correct! I pay with my parents credit card" but that is clearly wrong as it lacks the apostrophe.
Yeah, JimNolt reported the same above. I think it's Duolingo acting up rather than an error in the lesson inputs. Have seen the same for other sentences, and in other courses as well.
Thanks. Sometimes it marks me correct but then offers an alternative translation that is identical to that which I gave, which I assume is also some kind of internal glitch.
Yup. We average well over 500 error reports per months about it, across various sentences, and there's absolutely zero we can do about it. :( It's been reported internally - repeatedly - and there does not appear to be a solution in sight.
As long as English-speakers aren't testing their English grammar, I imagine this is more of a problem for Swedes learning English with the same sentences.