When Jon fights off the other three trainees defending Sam, one of them says that he yields, while holding his sword. In the exact next shot, his sword is on the ground several feet away from him, without sufficient time to drop it.
After a knight is killed at the tournament he is seen being easily dragged away by two average sized men. Mounted knights at tournaments wear the heaviest armor. Fully dressed he should weigh close to 200 kg (around 400 lbs). Not something that can be easily dragged through the sand by just two people.
Knights fully armored for jousting weighed close to 200 kg (400 lbs). A man the size of Gregor "The Mountain" Clegane would weigh even more than that. The horses shown in the tournament would simply collapse under such weight. Armored knights (e.g. in Europe) used MUCH larger horses.
In Bran's dream he is about to shoot at a target when the three-eyed crow flies across. We see in closeup that the forefinger of his shooting glove is
twisted under the bowstring, which would spoil the loose.
The knights in the tournament ride on the wrong side of the railing. Because most people are right-handed, the knights would ride on the left side of the railing. This sets up more direct access to the opponents body with a lance without having to reach across your own body. This is why traffic drives on the left side of the road in England to this day.