Program: 57921
Project: 57921
Buggy source:
@EventHandler(priority=EventPriority.HIGHEST,ignoreCancelled=true) public void onBlockPistonRetract(BlockPistonRetractEvent event){
  Block block=event.getBlock();
  Location location=BukkitUtil.getLocation(block.getLocation());
  PlotArea area=location.getPlotArea();
  if (area == null) {
    if (!PS.get().hasPlotArea(location.getWorld())) {
      return;
    }
    if (this.pistonBlocks) {
      try {
        for (        Block pulled : event.getBlocks()) {
          location=BukkitUtil.getLocation(pulled.getLocation());
          if (location.getPlotArea() != null) {
            event.setCancelled(true);
            return;
          }
        }
      }
 catch (      Throwable e) {
        this.pistonBlocks=false;
      }
    }
    if (!this.pistonBlocks && block.getType() != Material.PISTON_BASE) {
      BlockFace dir=event.getDirection();
      location=BukkitUtil.getLocation(block.getLocation().add(dir.getModX() * 2,dir.getModY() * 2,dir.getModZ() * 2));
      if (location.getPlotArea() != null) {
        event.setCancelled(true);
        return;
      }
    }
    return;
  }
  Plot plot=area.getOwnedPlot(location);
  if (this.pistonBlocks) {
    try {
      for (      Block pulled : event.getBlocks()) {
        location=BukkitUtil.getLocation(pulled.getLocation());
        if (!area.contains(location.getX(),location.getZ())) {
          event.setCancelled(true);
          return;
        }
        Plot newPlot=area.getOwnedPlot(location);
        if (!Objects.equals(plot,newPlot)) {
          event.setCancelled(true);
          return;
        }
      }
    }
 catch (    Throwable e) {
      this.pistonBlocks=false;
    }
  }
  if (!this.pistonBlocks && block.getType() != Material.PISTON_BASE) {
    BlockFace dir=event.getDirection();
    location=BukkitUtil.getLocation(block.getLocation().add(dir.getModX() * 2,dir.getModY() * 2,dir.getModZ() * 2));
    if (!area.contains(location)) {
      event.setCancelled(true);
      return;
    }
    Plot newPlot=area.getOwnedPlot(location);
    if (!Objects.equals(plot,newPlot)) {
      event.setCancelled(true);
    }
  }
}

Fixed version (ground truth):
@EventHandler(priority=EventPriority.HIGHEST,ignoreCancelled=true) public void onBlockPistonRetract(BlockPistonRetractEvent event){
  Block block=event.getBlock();
  Location location=BukkitUtil.getLocation(block.getLocation());
  PlotArea area=location.getPlotArea();
  if (area == null) {
    if (!PS.get().hasPlotArea(location.getWorld())) {
      return;
    }
    if (this.pistonBlocks) {
      try {
        for (        Block pulled : event.getBlocks()) {
          location=BukkitUtil.getLocation(pulled.getLocation());
          if (location.getPlotArea() != null) {
            event.setCancelled(true);
            return;
          }
        }
      }
 catch (      Throwable ignored) {
        this.pistonBlocks=false;
      }
    }
    if (!this.pistonBlocks && block.getType() != Material.PISTON_BASE) {
      BlockFace dir=event.getDirection();
      location=BukkitUtil.getLocation(block.getLocation().add(dir.getModX() * 2,dir.getModY() * 2,dir.getModZ() * 2));
      if (location.getPlotArea() != null) {
        event.setCancelled(true);
        return;
      }
    }
    return;
  }
  Plot plot=area.getOwnedPlot(location);
  if (this.pistonBlocks) {
    try {
      for (      Block pulled : event.getBlocks()) {
        location=BukkitUtil.getLocation(pulled.getLocation());
        if (!area.contains(location.getX(),location.getZ())) {
          event.setCancelled(true);
          return;
        }
        Plot newPlot=area.getOwnedPlot(location);
        if (!Objects.equals(plot,newPlot)) {
          event.setCancelled(true);
          return;
        }
      }
    }
 catch (    Throwable ignored) {
      this.pistonBlocks=false;
    }
  }
  if (!this.pistonBlocks && block.getType() != Material.PISTON_BASE) {
    BlockFace dir=event.getDirection();
    location=BukkitUtil.getLocation(block.getLocation().add(dir.getModX() * 2,dir.getModY() * 2,dir.getModZ() * 2));
    if (!area.contains(location)) {
      event.setCancelled(true);
      return;
    }
    Plot newPlot=area.getOwnedPlot(location);
    if (!Objects.equals(plot,newPlot)) {
      event.setCancelled(true);
    }
  }
}