Program: 158429
Project: 158429
Buggy source:
@Override public boolean apply(Game game,Ability source){
  Player controller=game.getPlayer(source.getControllerId());
  if (controller != null) {
    UUID sourceId=source.getSourceId();
    FilterControlledCreaturePermanent filter=new FilterControlledCreaturePermanent("String_Node_Str" + meldWithName);
    filter.add(new NamePredicate(meldWithName));
    TargetPermanent target=new TargetControlledCreaturePermanent(filter);
    Set<UUID> meldWithList=target.possibleTargets(sourceId,source.getControllerId(),game);
    UUID meldWithId;
    if (meldWithList.size() == 1) {
      meldWithId=meldWithList.iterator().next();
    }
 else {
      controller.choose(Outcome.BoostCreature,target,sourceId,game);
      meldWithId=target.getFirstTarget();
    }
    Permanent sourcePermanent=game.getPermanent(sourceId);
    Permanent meldWithPermanent=game.getPermanent(meldWithId);
    sourcePermanent.moveToExile(null,"String_Node_Str",sourceId,game);
    meldWithPermanent.moveToExile(null,"String_Node_Str",sourceId,game);
    Card sourceCard=game.getExile().getCard(sourceId,game);
    Card meldWithCard=game.getExile().getCard(meldWithId,game);
    if (!sourceCard.isCopy() && !meldWithCard.isCopy()) {
      meldCard.setOwnerId(controller.getId());
      meldCard.setTopHalfCard(meldWithCard,game);
      meldCard.setbottomHalfCard(sourceCard,game);
      meldCard.setMelded(true);
      game.addMeldCard(meldCard.getId(),meldCard);
      game.getState().addCard(meldCard);
      meldCard.moveToZone(Zone.BATTLEFIELD,sourceId,game,false);
    }
    return true;
  }
  return false;
}

Fixed version (ground truth):
@Override public boolean apply(Game game,Ability source){
  Player controller=game.getPlayer(source.getControllerId());
  if (controller != null) {
    UUID sourceId=source.getSourceId();
    FilterControlledCreaturePermanent filter=new FilterControlledCreaturePermanent("String_Node_Str" + meldWithName);
    filter.add(new NamePredicate(meldWithName));
    TargetPermanent target=new TargetControlledCreaturePermanent(filter);
    Set<UUID> meldWithList=target.possibleTargets(sourceId,source.getControllerId(),game);
    if (meldWithList.isEmpty()) {
      return false;
    }
    UUID meldWithId;
    if (meldWithList.size() == 1) {
      meldWithId=meldWithList.iterator().next();
    }
 else {
      controller.choose(Outcome.BoostCreature,target,sourceId,game);
      meldWithId=target.getFirstTarget();
    }
    Permanent sourcePermanent=game.getPermanent(sourceId);
    Permanent meldWithPermanent=game.getPermanent(meldWithId);
    if (sourcePermanent != null && meldWithPermanent != null) {
      sourcePermanent.moveToExile(null,"String_Node_Str",sourceId,game);
      meldWithPermanent.moveToExile(null,"String_Node_Str",sourceId,game);
      Card sourceCard=game.getExile().getCard(sourceId,game);
      Card meldWithCard=game.getExile().getCard(meldWithId,game);
      if (!sourceCard.isCopy() && !meldWithCard.isCopy()) {
        meldCard.setOwnerId(controller.getId());
        meldCard.setTopHalfCard(meldWithCard,game);
        meldCard.setbottomHalfCard(sourceCard,game);
        meldCard.setMelded(true);
        game.addMeldCard(meldCard.getId(),meldCard);
        game.getState().addCard(meldCard);
        meldCard.moveToZone(Zone.BATTLEFIELD,sourceId,game,false);
      }
      return true;
    }
  }
  return false;
}