Every movie or TV series has some mistakes. The entire piece is shot over a long time, which makes these mistakes unavoidable. Mostly, the editing team lets it skip, as they cannot edit every shot. One such case is from season 5 when blood reappears on a sword after it is wiped.
Another one is from season one episode 4 when the sword magically jumps in front of him. From season 5 episode 4, we see that there should be many dead bodies. However, when the scene pans, there are only a few of them. These are some mistakes that we picked up.
One mistake from Game of Thones that people missed was from Season 5, Episode 9 when during a sword fight when blood reappears after being wiped off. From Season 1, Episode 4 Grenn prepares for a skirmish when all of a sudden his sword jumps several feet from out in front of him. From Season 5, Episode 4 there is a scene in which there are a lot of dead bodies from The Sons of Harpy but then it pans and there are a lot less dead bodies then what should have been there.
There are also numerous times during the course of the series when certain males and females are associated and given the projection that they were part of another clan or house. There were also obvious mistakes that people who read the George R.R. Martin books would have seen by the television series not following the true course of the Martin novels. There are certainly more mistakes that people didnt and did notice during the series. A lot of them were mistakes that were made during the final edits and cuts of the productions.