Program: 101817
Project: 101817
Buggy source:
public boolean checkFlight(Player player,Distance distance){
  if (distance.getYDifference() > 400) {
    return false;
  }
  String name=player.getName();
  double y1=distance.fromY();
  double y2=distance.toY();
  if (!isMovingExempt(player) && !Utilities.isInWater(player) && !Utilities.canStand(player.getLocation().getBlock())&& Utilities.cantStandAt(player.getLocation().add(0,-1,0).getBlock())&& Utilities.cantStandAt(player.getLocation().add(0,-2,0).getBlock())) {
    Block block=player.getLocation().getBlock();
    if (block.getRelative(BlockFace.NORTH).isLiquid() || block.getRelative(BlockFace.SOUTH).isLiquid() || block.getRelative(BlockFace.EAST).isLiquid()|| block.getRelative(BlockFace.WEST).isLiquid()) {
      if (y1 < y2) {
        return distance.getYDifference() > magic.WATER_CLIMB_MAX;
      }
    }
 else     if (y1 == y2 || y1 < y2) {
      if (y1 == y2) {
        if (block.getRelative(BlockFace.NORTH).getTypeId() == 43 || block.getRelative(BlockFace.NORTH).getTypeId() == 44 || block.getRelative(BlockFace.SOUTH).getTypeId() == 43 || block.getRelative(BlockFace.SOUTH).getTypeId() == 44 || block.getRelative(BlockFace.EAST).getTypeId() == 43 || block.getRelative(BlockFace.EAST).getTypeId() == 44 || block.getRelative(BlockFace.WEST).getTypeId() == 43 || block.getRelative(BlockFace.WEST).getTypeId() == 44) {
          return false;
        }
 else         if (player.isSneaking() && Utilities.isStair(block.getRelative(BlockFace.NORTH)) || Utilities.isStair(block.getRelative(BlockFace.SOUTH)) || Utilities.isStair(block.getRelative(BlockFace.EAST)) || Utilities.isStair(block.getRelative(BlockFace.WEST))) {
          return false;
        }
      }
      int violation=flightViolation.containsKey(name) ? flightViolation.get(name) + 1 : 1;
      increment(player,flightViolation,violation);
      if (violation > magic.FLIGHT_LIMIT) {
        return true;
      }
 else {
        return false;
      }
    }
  }
  flightViolation.put(name,0);
  return false;
}

Fixed version (ground truth):
public boolean checkFlight(Player player,Distance distance){
  if (distance.getYDifference() > 400) {
    return false;
  }
  String name=player.getName();
  double y1=distance.fromY();
  double y2=distance.toY();
  if (!isMovingExempt(player) && !Utilities.isInWater(player) && !Utilities.canStand(player.getLocation().getBlock())&& Utilities.cantStandAt(player.getLocation().add(0,-1,0).getBlock())&& Utilities.cantStandAt(player.getLocation().add(0,-2,0).getBlock())) {
    Block block=player.getLocation().getBlock();
    if (block.getRelative(BlockFace.NORTH).isLiquid() || block.getRelative(BlockFace.SOUTH).isLiquid() || block.getRelative(BlockFace.EAST).isLiquid()|| block.getRelative(BlockFace.WEST).isLiquid()) {
      if (y1 < y2) {
        return distance.getYDifference() > magic.WATER_CLIMB_MAX;
      }
    }
 else     if (y1 == y2 || y1 < y2) {
      if (y1 == y2) {
        if (block.getRelative(BlockFace.NORTH).getTypeId() == 43 || block.getRelative(BlockFace.NORTH).getTypeId() == 44 || block.getRelative(BlockFace.SOUTH).getTypeId() == 43 || block.getRelative(BlockFace.SOUTH).getTypeId() == 44 || block.getRelative(BlockFace.EAST).getTypeId() == 43 || block.getRelative(BlockFace.EAST).getTypeId() == 44 || block.getRelative(BlockFace.WEST).getTypeId() == 43 || block.getRelative(BlockFace.WEST).getTypeId() == 44) {
          return false;
        }
 else         if (player.isSneaking() && (Utilities.isStair(block.getRelative(BlockFace.NORTH)) || Utilities.isStair(block.getRelative(BlockFace.SOUTH)) || Utilities.isStair(block.getRelative(BlockFace.EAST))|| Utilities.isStair(block.getRelative(BlockFace.WEST))|| Utilities.isStair(block.getRelative(BlockFace.NORTH_EAST))|| Utilities.isStair(block.getRelative(BlockFace.SOUTH_EAST))|| Utilities.isStair(block.getRelative(BlockFace.SOUTH_WEST))|| Utilities.isStair(block.getRelative(BlockFace.NORTH_WEST)))) {
          return false;
        }
      }
      int violation=flightViolation.containsKey(name) ? flightViolation.get(name) + 1 : 1;
      increment(player,flightViolation,violation);
      if (violation > magic.FLIGHT_LIMIT) {
        return true;
      }
 else {
        return false;
      }
    }
  }
  flightViolation.put(name,0);
  return false;
}