I wrote, "This is my parents' fridge," and it said that it is "almost correct" and "corrected" it to "parents fridge." It also said that another possible translation is, "This is my parents' refrigerator."
I don't really know how to report this issue because it counted it as correct…
The same problem was mentioned above in the comments. The accepted answers all have apostrophe when needed. It's understandable that without it it's accepted, as Duo doesn't mark interpunction, but I have absolutely no idea why it suggests a version without an apostrophe.
And the freewrite reports are full of comments about it, some of them really long... We would love to fix it, but I don't think there's anything that could be done from our side.
That is odd, maybe it is glitched. I have had some really random glitches in the past. For example, one time when I was doing a "strengthen skills" lesson, it literally switched from Polish to Esperanto half way through. I think because I left it alone for a few hours and it somehow reset even though it saved half of the progress from Polish for the Esperanto lesson. I wish I finished it so I could have seen what skills it would have improved xD
As it has also been discussed, this is some kind of a really weird bug. Because we haven't put "my parents fridge" among the correct answers. The answers in the Incubator all have the apostrophe where needed. And there is a huge list of reports complaining about what you just wrote - you write a correct answer, which is (obviously) considered correct on our side, but somehow the programme shows you that you made a typo. I have no clue why and there's not much I can do - I think I will write a ticket to Duolingo, but as this is a rather minor issue (it's annoying, but it accepts the answer), I wouldn't expect them to act soon.