Program: 158812
Project: 158812
Buggy source:
@Override public boolean apply(Game game,Ability source){
  StackObject stackObject=game.getStack().getStackObject(source.getFirstTarget());
  MageObject sourceObject=game.getObject(source.getSourceId());
  if (stackObject != null && sourceObject != null) {
    Targets targets=new Targets();
    Ability sourceAbility;
    MageObject oldTarget=null;
    if (stackObject instanceof Spell) {
      Spell spell=(Spell)stackObject;
      sourceAbility=spell.getSpellAbility();
    }
 else     if (stackObject instanceof StackAbility) {
      StackAbility stackAbility=(StackAbility)stackObject;
      sourceAbility=stackAbility;
    }
 else {
      return false;
    }
    for (    UUID modeId : sourceAbility.getModes().getSelectedModes()) {
      sourceAbility.getModes().setActiveMode(modeId);
      targets.addAll(sourceAbility.getTargets());
    }
    boolean twoTimesTarget=false;
    if (targets.size() == 1 && targets.get(0).getTargets().size() == 1) {
      Target target=targets.get(0);
      if (target.canTarget(stackObject.getControllerId(),source.getSourceId(),sourceAbility,game)) {
        oldTarget=game.getObject(targets.getFirstTarget());
        target.clearChosen();
        target.addTarget(source.getSourceId(),stackObject.getStackAbility(),game);
      }
    }
 else {
      Player player=game.getPlayer(source.getControllerId());
      for (      Target target : targets) {
        for (        UUID targetId : target.getTargets()) {
          MageObject object=game.getObject(targetId);
          String name;
          if (object == null) {
            Player targetPlayer=game.getPlayer(targetId);
            name=targetPlayer.getLogName();
          }
 else {
            name=object.getLogName();
          }
          if (!targetId.equals(source.getSourceId()) && target.getTargets().contains(source.getSourceId())) {
            twoTimesTarget=true;
            continue;
          }
          if (name != null && player.chooseUse(Outcome.Neutral,"String_Node_Str" + name + "String_Node_Str"+ sourceObject.getLogName()+ "String_Node_Str",source,game)) {
            if (target.canTarget(stackObject.getControllerId(),source.getSourceId(),sourceAbility,game)) {
              oldTarget=game.getObject(targets.getFirstTarget());
              target.remove(targetId);
              target.addTarget(source.getSourceId(),stackObject.getStackAbility(),game);
              break;
            }
          }
        }
      }
    }
    if (oldTarget != null) {
      game.informPlayers(sourceObject.getLogName() + "String_Node_Str" + stackObject.getLogName()+ "String_Node_Str"+ oldTarget.getLogName()+ "String_Node_Str"+ sourceObject.getLogName());
    }
 else {
      if (twoTimesTarget) {
        game.informPlayers(sourceObject.getLogName() + "String_Node_Str" + sourceObject.getLogName()+ "String_Node_Str"+ stackObject.getLogName());
      }
 else {
        game.informPlayers(sourceObject.getLogName() + "String_Node_Str" + sourceObject.getLogName()+ "String_Node_Str"+ stackObject.getLogName());
      }
    }
    return true;
  }
  return false;
}

Fixed version (ground truth):
@Override public boolean apply(Game game,Ability source){
  StackObject stackObject=game.getStack().getStackObject(source.getFirstTarget());
  MageObject sourceObject=game.getObject(source.getSourceId());
  if (stackObject != null && sourceObject != null) {
    Targets targets=new Targets();
    Ability sourceAbility;
    MageObject oldTarget=null;
    if (stackObject instanceof Spell) {
      Spell spell=(Spell)stackObject;
      sourceAbility=spell.getSpellAbility();
    }
 else     if (stackObject instanceof StackAbility) {
      StackAbility stackAbility=(StackAbility)stackObject;
      sourceAbility=stackAbility;
    }
 else {
      return false;
    }
    for (    UUID modeId : sourceAbility.getModes().getSelectedModes()) {
      sourceAbility.getModes().setActiveMode(modeId);
      targets.addAll(sourceAbility.getTargets());
    }
    boolean twoTimesTarget=false;
    if (targets.size() == 1 && targets.get(0).getTargets().size() == 1) {
      Target target=targets.get(0);
      if (target.canTarget(stackObject.getControllerId(),source.getSourceId(),sourceAbility,game)) {
        oldTarget=game.getObject(targets.getFirstTarget());
        target.clearChosen();
        target.addTarget(source.getSourceId(),stackObject.getStackAbility(),game);
      }
    }
 else {
      Player controller=game.getPlayer(source.getControllerId());
      boolean validTargets=false;
      do {
        for (        Target target : targets) {
          for (          UUID targetId : target.getTargets()) {
            MageObject object=game.getObject(targetId);
            String name;
            if (object == null) {
              Player targetPlayer=game.getPlayer(targetId);
              name=targetPlayer.getLogName();
            }
 else {
              name=object.getLogName();
            }
            if (!targetId.equals(source.getSourceId()) && target.getTargets().contains(source.getSourceId())) {
              twoTimesTarget=true;
              continue;
            }
            if (target.canTarget(stackObject.getControllerId(),source.getSourceId(),sourceAbility,game)) {
              validTargets=true;
              if (name != null && controller.chooseUse(Outcome.Neutral,"String_Node_Str" + name + "String_Node_Str"+ sourceObject.getLogName()+ "String_Node_Str",source,game)) {
                oldTarget=game.getObject(targetId);
                target.remove(targetId);
                target.addTarget(source.getSourceId(),stackObject.getStackAbility(),game);
                break;
              }
            }
          }
          if (oldTarget != null) {
            break;
          }
        }
        if (oldTarget == null) {
          game.informPlayer(controller,"String_Node_Str");
        }
      }
 while (validTargets && oldTarget == null);
    }
    if (oldTarget != null) {
      game.informPlayers(sourceObject.getLogName() + "String_Node_Str" + stackObject.getLogName()+ "String_Node_Str"+ oldTarget.getLogName()+ "String_Node_Str"+ sourceObject.getLogName());
    }
 else {
      if (twoTimesTarget) {
        game.informPlayers(sourceObject.getLogName() + "String_Node_Str" + sourceObject.getLogName()+ "String_Node_Str"+ stackObject.getLogName());
      }
 else {
        game.informPlayers(sourceObject.getLogName() + "String_Node_Str" + sourceObject.getLogName()+ "String_Node_Str"+ stackObject.getLogName());
      }
    }
    return true;
  }
  return false;
}