Program: 57925
Project: 57925
Buggy source:
@EventHandler(priority=EventPriority.HIGHEST,ignoreCancelled=true) public void blockCreate(BlockPlaceEvent event){
  Location loc=BukkitUtil.getLocation(event.getBlock().getLocation());
  PlotArea area=loc.getPlotArea();
  if (area == null) {
    return;
  }
  Player player=event.getPlayer();
  PlotPlayer pp=BukkitUtil.getPlayer(player);
  Plot plot=area.getPlotAbs(loc);
  if (plot != null) {
    if (!plot.hasOwner()) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_UNOWNED)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_UNOWNED);
        event.setCancelled(true);
        return;
      }
    }
 else     if (!plot.isAdded(pp.getUUID())) {
      Optional<HashSet<PlotBlock>> place=plot.getFlag(Flags.PLACE);
      Block block=event.getBlock();
      if ((place.isPresent() && !place.get().contains(new PlotBlock((short)block.getTypeId(),block.getData()))) && !Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_OTHER)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_OTHER);
        event.setCancelled(true);
        return;
      }
    }
 else     if (Settings.DONE_RESTRICTS_BUILDING && plot.getFlags().containsKey(Flags.DONE)) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_OTHER)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_OTHER);
        event.setCancelled(true);
        return;
      }
    }
    if (plot.getFlag(Flags.DISABLE_PHYSICS).or(false)) {
      Block block=event.getBlockPlaced();
      if (block.getType().hasGravity()) {
        sendBlockChange(block.getLocation(),block.getType(),block.getData());
      }
    }
    if (loc.getY() > area.MAX_BUILD_HEIGHT && loc.getY() < area.MIN_BUILD_HEIGHT && !Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_HEIGHTLIMIT)) {
      event.setCancelled(true);
      MainUtil.sendMessage(pp,C.HEIGHT_LIMIT.s().replace("String_Node_Str","String_Node_Str" + area.MAX_BUILD_HEIGHT));
    }
  }
 else   if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_OTHER)) {
    MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_ROAD);
    event.setCancelled(true);
  }
}

Fixed version (ground truth):
@EventHandler(priority=EventPriority.HIGHEST,ignoreCancelled=true) public void blockCreate(BlockPlaceEvent event){
  Location loc=BukkitUtil.getLocation(event.getBlock().getLocation());
  PlotArea area=loc.getPlotArea();
  if (area == null) {
    return;
  }
  Player player=event.getPlayer();
  PlotPlayer pp=BukkitUtil.getPlayer(player);
  Plot plot=area.getPlotAbs(loc);
  if (plot != null) {
    if (!plot.hasOwner()) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_UNOWNED)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_UNOWNED);
        event.setCancelled(true);
        return;
      }
    }
 else     if (!plot.isAdded(pp.getUUID())) {
      Optional<HashSet<PlotBlock>> place=plot.getFlag(Flags.PLACE);
      Block block=event.getBlock();
      if ((place.isPresent() && !place.get().contains(new PlotBlock((short)block.getTypeId(),block.getData()))) && !Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_OTHER)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_OTHER);
        event.setCancelled(true);
        return;
      }
    }
 else     if (Settings.DONE_RESTRICTS_BUILDING && plot.getFlags().containsKey(Flags.DONE)) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_OTHER)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_OTHER);
        event.setCancelled(true);
        return;
      }
    }
    if (plot.getFlag(Flags.DISABLE_PHYSICS).or(false)) {
      Block block=event.getBlockPlaced();
      if (block.getType().hasGravity()) {
        sendBlockChange(block.getLocation(),block.getType(),block.getData());
      }
    }
    if (loc.getY() > area.MAX_BUILD_HEIGHT && loc.getY() < area.MIN_BUILD_HEIGHT && !Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_HEIGHTLIMIT)) {
      event.setCancelled(true);
      MainUtil.sendMessage(pp,C.HEIGHT_LIMIT.s().replace("String_Node_Str",String.valueOf(area.MAX_BUILD_HEIGHT)));
    }
  }
 else   if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_OTHER)) {
    MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_ROAD);
    event.setCancelled(true);
  }
}