Program: 81416
Project: 81416
Buggy source:
public void actionPerformed(ActionEvent event){
  if (Jail.timeUpdateRunning)   return;
  Jail.timeUpdateRunning=true;
  if (UpdateTime == 0) {
    getServer().getScheduler().scheduleSyncDelayedTask(Jail.instance,new Runnable(){
      public void run(){
        for (        JailPrisoner prisoner : prisoners.values()) {
          Player player=getServer().getPlayer(prisoner.getName());
          if (prisoner.getRemainingTime() > 0 && (player != null || (prisoner.getJail() != null && prisoner.getJail().getSettings().getBoolean(Setting.CountdownTimeWhenOffline)))) {
            prisoner.setRemainingTime(prisoner.getRemainingTime() - 1);
            InputOutput.UpdatePrisoner(prisoner);
          }
 else           if (player != null && prisoner.getRemainingTime() == 0 && prisoner.offlinePending() == false) {
            PrisonerManager.UnJail(prisoner,player);
          }
          if (player != null) {
            if (prisoner.getJail().getSettings().getDouble(Setting.MaximumAFKTime) > 0.0) {
              prisoner.setAFKTime(prisoner.getAFKTime() + 1);
              if (prisoner.getAFKTimeMinutes() > prisoner.getJail().getSettings().getDouble(Setting.MaximumAFKTime)) {
                prisoner.setAFKTime(0);
                player.kickPlayer(prisoner.getJail().getSettings().getString(Setting.MessageAFKKick));
              }
            }
          }
        }
      }
    }
,1L);
    UpdateTime++;
  }
 else {
    UpdateTime++;
    if (UpdateTime > 9) {
      UpdateTime=0;
    }
  }
  for (  JailPrisoner prisoner : prisoners.values()) {
    Player player=getServer().getPlayer(prisoner.getName());
    if (player == null)     continue;
    if (!prisoner.getJail().getSettings().getBoolean(Setting.EnableFoodControl))     continue;
    int minfood=prisoner.getJail().getSettings().getInt(Setting.FoodControlMinimumFood);
    int maxfood=prisoner.getJail().getSettings().getInt(Setting.FoodControlMaximumFood);
    if (player.getFoodLevel() < minfood || player.getFoodLevel() > maxfood) {
      player.setFoodLevel((minfood + maxfood) / 2);
    }
  }
  Jail.timeUpdateRunning=false;
}

Fixed version (ground truth):
public void actionPerformed(ActionEvent event){
  if (Jail.timeUpdateRunning)   return;
  Jail.timeUpdateRunning=true;
  if (UpdateTime == 0) {
    getServer().getScheduler().scheduleSyncDelayedTask(Jail.instance,new Runnable(){
      public void run(){
        for (        JailPrisoner prisoner : prisoners.values()) {
          Player player=getServer().getPlayer(prisoner.getName());
          if (prisoner.getRemainingTime() > 0 && (player != null || (prisoner.getJail() != null && prisoner.getJail().getSettings().getBoolean(Setting.CountdownTimeWhenOffline)))) {
            prisoner.setRemainingTime(prisoner.getRemainingTime() - 1);
            InputOutput.UpdatePrisoner(prisoner);
          }
 else           if (player != null && prisoner.getRemainingTime() == 0 && prisoner.offlinePending() == false) {
            PrisonerManager.UnJail(prisoner,player);
          }
          if (player != null && prisoner.getJail() != null) {
            if (prisoner.getJail().getSettings().getDouble(Setting.MaximumAFKTime) > 0.0) {
              prisoner.setAFKTime(prisoner.getAFKTime() + 1);
              if (prisoner.getAFKTimeMinutes() > prisoner.getJail().getSettings().getDouble(Setting.MaximumAFKTime)) {
                prisoner.setAFKTime(0);
                player.kickPlayer(prisoner.getJail().getSettings().getString(Setting.MessageAFKKick));
              }
            }
          }
        }
      }
    }
,1L);
    UpdateTime++;
  }
 else {
    UpdateTime++;
    if (UpdateTime > 9) {
      UpdateTime=0;
    }
  }
  for (  JailPrisoner prisoner : prisoners.values()) {
    Player player=getServer().getPlayer(prisoner.getName());
    if (player == null || prisoner.getJail() == null)     continue;
    if (!prisoner.getJail().getSettings().getBoolean(Setting.EnableFoodControl))     continue;
    int minfood=prisoner.getJail().getSettings().getInt(Setting.FoodControlMinimumFood);
    int maxfood=prisoner.getJail().getSettings().getInt(Setting.FoodControlMaximumFood);
    if (player.getFoodLevel() < minfood || player.getFoodLevel() > maxfood) {
      player.setFoodLevel((minfood + maxfood) / 2);
    }
  }
  Jail.timeUpdateRunning=false;
}