There's a lot reasons why the ending could be wrong. The author may just be tired of the series and is quickly trying to wrap things up. As a fan, you might not want the end to be now so it comes off as wrong. But from what I've seen the most from the books I've read, it's rushing. Trying to tie everything up and trying to force a happy ending. Even if it means doing something with a character that that particular character wouldn't do. The few times I've finished what I started the ending is either open-ended so that the reader can form their own opinions or the main character either dies or loses everything and has no will to keep going on.