Champions Seen on Minimap at an Incorrect Position
This bug has been around for quite some time. I've been playing since season 2 and can remember seeing it as early as season 3/4.
Sometimes an enemy champion appears briefly on the mini-map at a random location. I just died because of this, because I moved my camera off of my character while I finished a camp, and Lee Sin magically came over the wall one second after I saw him on the other side of the map.
This should be a high priority bug. It's gotten the better of me quite a number of times.