"Mae fy wyres yn hoffi moron" is marked as wrong but there is no option to report it as a problem.
It is definitely in the database as an accepted answer. If it is rejected again, please take a screenshot and attach it to a 'Duolingo bug report' so that Duo staff can investigate.
I think the confusion has arisen because the dictation version marks 'yn' as wrong, it's simply a detail of the audio, just one of those duo things. On the whole the audio is excellent and this one is clear on the tortoise version.
Wyres is the female version of ŵyr ("grandson, grandchild"), which is cognate with Latin puer ("child, boy"), source of English puerile.
Is "moron" one of those nouns that doesn't change really between the singular and plural words?
It's still marking Mae fy wyres yn hoffi moron as wrong.
Is it still bugged?
It is still in the accepted answers. If you use the app, check that you have the latest version. Otherwise, please raise a 'Duolingo bug report', attaching a screenshot of the rejection if possible.