Program: 10321
Project: 10321
Buggy source:
@EventHandler public void yaml(ReplaceableTagEvent event){
  if (!event.matches("String_Node_Str"))   return;
  if (!event.hasNameContext() || !event.hasTypeContext()) {
    dB.echoError("String_Node_Str" + event.raw_tag + "String_Node_Str");
    return;
  }
  String id=event.getNameContext();
  String path=event.getTypeContext();
  if (!yamls.containsKey(id.toUpperCase())) {
    dB.echoError("String_Node_Str" + event.raw_tag + "String_Node_Str"+ "String_Node_Str");
    return;
  }
  Attribute attribute=new Attribute(event.raw_tag,event.getScriptEntry());
  attribute.fulfill(1);
  if (attribute.startsWith("String_Node_Str")) {
    event.setReplaced(new Element(getYaml(id).contains(path)).getAttribute(attribute.fulfill(1)));
    return;
  }
  if (attribute.startsWith("String_Node_Str")) {
    attribute.fulfill(1);
    if (attribute.startsWith("String_Node_Str")) {
      List<String> list=getYaml(id).getStringList(path);
      if (list == null) {
        dB.echoDebug(event.getScriptEntry(),"String_Node_Str" + event.raw_tag + "String_Node_Str");
        event.setReplaced(new Element("String_Node_Str").getAttribute(attribute));
        return;
      }
      event.setReplaced(new dList(list).getAttribute(attribute.fulfill(1)));
      return;
    }
    String value=getYaml(id).getString(path);
    if (value == null) {
      dB.echoDebug(event.getScriptEntry(),"String_Node_Str" + event.raw_tag + "String_Node_Str");
      event.setReplaced(new Element("String_Node_Str").getAttribute(attribute));
      return;
    }
 else {
      event.setReplaced(new Element(value).getAttribute(attribute.fulfill(1)));
      return;
    }
  }
  if (attribute.startsWith("String_Node_Str")) {
    ConfigurationSection section=getYaml(id).getConfigurationSection(path);
    if (section == null) {
      dB.echoDebug(event.getScriptEntry(),"String_Node_Str" + event.raw_tag + "String_Node_Str");
      event.setReplaced(new Element("String_Node_Str").getAttribute(attribute.fulfill(1)));
      return;
    }
    Set<String> keys=section.getKeys(false);
    if (keys == null) {
      dB.echoDebug(event.getScriptEntry(),"String_Node_Str" + event.raw_tag + "String_Node_Str");
      event.setReplaced(new Element("String_Node_Str").getAttribute(attribute.fulfill(1)));
      return;
    }
 else {
      ArrayList<String> list=new ArrayList<String>();
      list.addAll(keys);
      event.setReplaced(new dList(list).getAttribute(attribute.fulfill(1)));
      return;
    }
  }
}

Fixed version (ground truth):
@EventHandler public void yaml(ReplaceableTagEvent event){
  if (!event.matches("String_Node_Str"))   return;
  if (!event.hasNameContext() || !event.hasTypeContext()) {
    dB.echoError("String_Node_Str" + event.raw_tag + "String_Node_Str");
    return;
  }
  String id=event.getNameContext();
  String path=event.getTypeContext();
  if (!yamls.containsKey(id.toUpperCase())) {
    dB.echoError("String_Node_Str" + event.raw_tag + "String_Node_Str"+ "String_Node_Str");
    return;
  }
  Attribute attribute=new Attribute(event.raw_tag,event.getScriptEntry());
  attribute.fulfill(1);
  if (attribute.startsWith("String_Node_Str")) {
    event.setReplaced(new Element(getYaml(id).contains(path)).getAttribute(attribute.fulfill(1)));
    return;
  }
  if (attribute.startsWith("String_Node_Str")) {
    attribute.fulfill(1);
    if (attribute.startsWith("String_Node_Str")) {
      List<String> list=getYaml(id).getStringList(path);
      if (list == null) {
        dB.echoDebug(event.getScriptEntry(),"String_Node_Str" + event.raw_tag + "String_Node_Str");
        event.setReplaced(new Element("String_Node_Str").getAttribute(attribute));
        return;
      }
      event.setReplaced(new dList(list).getAttribute(attribute.fulfill(1)));
      return;
    }
    String value=getYaml(id).getString(path);
    if (value == null) {
      dB.echoDebug(event.getScriptEntry(),"String_Node_Str" + event.raw_tag + "String_Node_Str");
      event.setReplaced(new Element("String_Node_Str").getAttribute(attribute));
      return;
    }
 else {
      event.setReplaced(new Element(value).getAttribute(attribute));
      return;
    }
  }
  if (attribute.startsWith("String_Node_Str")) {
    ConfigurationSection section=getYaml(id).getConfigurationSection(path);
    if (section == null) {
      dB.echoDebug(event.getScriptEntry(),"String_Node_Str" + event.raw_tag + "String_Node_Str");
      event.setReplaced(new Element("String_Node_Str").getAttribute(attribute.fulfill(1)));
      return;
    }
    Set<String> keys=section.getKeys(false);
    if (keys == null) {
      dB.echoDebug(event.getScriptEntry(),"String_Node_Str" + event.raw_tag + "String_Node_Str");
      event.setReplaced(new Element("String_Node_Str").getAttribute(attribute.fulfill(1)));
      return;
    }
 else {
      ArrayList<String> list=new ArrayList<String>();
      list.addAll(keys);
      event.setReplaced(new dList(list).getAttribute(attribute.fulfill(1)));
      return;
    }
  }
}