This is an unreachable block inside this if statement. The nested if (this.getY() < entity.getY() + 12.0D) and (this.getY() > entity.getY() + 26.0D) cannot be true at the same time.

This seems to cause the Eye to never travel down, but it will continue to fly upwards if the player is above it.

Thanks for figuring this out. Fixed with 6dacd5f