High left flyers can be caused by all sorts of things, but one common cause is failing to complete the draw. Toward the end of the draw, the arrow has been drawn almost to full draw, and there should be a movement of the drawing elbow around toward the spine, so that a diagram of the draw viewed from above looks kind of like a "J". If you release the arrow before making the bottom of the J, it will impact to the left.
One possible cause of the high part of the miss can be if you allow your drawing elbow to drop down below the level of the arrow, because you get tired or sloppy. When your drawing elbow drops, you're pulling down on the nock end of the arrow, which inclines the arrow upward and causes a high miss.