Since the pool is still in the track and has not come out of the caps at the base or top. This is the only post that is flat. I am wondering if the post is defective
It is certainly not right. There have been folks here who have replaced an upright with water in the pool but I am not sure of your risk tolerance.
Did you get this pool from the pool factory? I would contact them asap & have them overnight you a new upright.
You’ll need to take the dirt away from the bottom of the post & take pics of it being level etc. You’ll need to do this anyway to replace it.