Program: 178496
Project: 178496
Buggy source:
@Override public void onKeyDown(KeyDownEvent event){
  final int keyCode=event.getNativeKeyCode();
  log.fine("String_Node_Str" + keyCode + "String_Node_Str"+ event.getNativeEvent().getKeyCode());
  Selection selection=getTextArea().getDocument().getSelection();
  if (selection.getRangeCount() > 0) {
    Range range=selection.getRangeAt(0);
    doStuff(range);
    Node startContainer=range.getStartContainer();
    int pos=0;
    if (Node.TEXT_NODE == startContainer.getNodeType()) {
      log.info("String_Node_Str");
      Text textNode=Text.as(startContainer);
      pos=range.getStartOffset();
    }
    Node endContainer=range.getEndContainer();
    if (Node.ELEMENT_NODE == endContainer.getNodeType() || Node.DOCUMENT_NODE == endContainer.getNodeType()) {
      log.info("String_Node_Str");
      pos=range.getEndOffset();
    }
    OperationTarget t=getTarget(range);
    List<Integer> path=t.getStartContainer();
    TreeOperation op=null;
    if (keyCode == 8) {
      if (pos == 0) {
        if (isNoteworthyPath(path)) {
          op=new TreeMergeParagraph(clientJupiter.getSiteId(),path.get(0),1,1);
          op.setPath(convertPath(path));
        }
      }
 else {
        pos=pos - 1;
        op=new TreeDeleteText(clientJupiter.getSiteId(),pos,convertPath(path));
      }
    }
 else     if (keyCode == 46) {
      final Node node=TreeHelper.getChildNodeFromLocator(TreeClientCallback.getUpdatedNativeNode(),convertPath(t.getStartContainer()));
      if (Node.TEXT_NODE == node.getNodeType()) {
        Text textNode=Text.as(node);
        if (textNode.getLength() == t.getStartOffset()) {
          Element sibling=textNode.getParentElement().getNextSiblingElement();
          if ((sibling != null) && (!sibling.getClassName().toLowerCase().contains("String_Node_Str"))) {
            path.set(0,path.get(0) + 1);
            op=new TreeMergeParagraph(clientJupiter.getSiteId(),path.get(0),1,1);
            op.setPath(convertPath(path));
          }
        }
 else {
          op=new TreeDeleteText(clientJupiter.getSiteId(),pos,convertPath(path));
        }
      }
 else       if (Node.ELEMENT_NODE == node.getNodeType()) {
        path.set(0,path.get(0) + 1);
        op=new TreeMergeParagraph(clientJupiter.getSiteId(),path.get(0),1,1);
        op.setPath(convertPath(path));
      }
    }
 else     if (keyCode == 13) {
      if (pos == 0 && !isNoteworthyPath(path.subList(1,path.size()))) {
        op=new TreeNewParagraph(clientJupiter.getSiteId(),pos);
        op.setPath(convertPath(path));
      }
 else {
        op=new TreeInsertParagraph(clientJupiter.getSiteId(),pos,convertPath(path));
      }
    }
    if (op != null) {
      clientJupiter.generate(op);
    }
  }
}

Fixed version (ground truth):
@Override public void onKeyDown(KeyDownEvent event){
  final int keyCode=event.getNativeKeyCode();
  log.fine("String_Node_Str" + keyCode + "String_Node_Str"+ event.getNativeEvent().getKeyCode());
  Selection selection=getTextArea().getDocument().getSelection();
  if (selection.getRangeCount() > 0) {
    Range range=selection.getRangeAt(0);
    doStuff(range);
    Node startContainer=range.getStartContainer();
    int pos=0;
    if (Node.TEXT_NODE == startContainer.getNodeType()) {
      log.info("String_Node_Str");
      Text textNode=Text.as(startContainer);
      pos=range.getStartOffset();
    }
    Node endContainer=range.getEndContainer();
    if (Node.ELEMENT_NODE == endContainer.getNodeType() || Node.DOCUMENT_NODE == endContainer.getNodeType()) {
      log.info("String_Node_Str");
      pos=range.getEndOffset();
    }
    OperationTarget t=getTarget(range);
    List<Integer> path=t.getStartContainer();
    TreeOperation op=null;
    if (keyCode == 8) {
      if (pos == 0) {
        if (isNoteworthyPath(path)) {
          op=new TreeMergeParagraph(clientJupiter.getSiteId(),path.get(0),1,1);
          op.setPath(convertPath(path));
        }
      }
 else {
        pos=pos - 1;
        op=new TreeDeleteText(clientJupiter.getSiteId(),pos,convertPath(path));
      }
    }
 else     if (keyCode == 46) {
      final Node node=TreeHelper.getChildNodeFromLocator(TreeClientCallback.getUpdatedNativeNode(),convertPath(t.getStartContainer()));
      if (Node.TEXT_NODE == node.getNodeType()) {
        Text textNode=Text.as(node);
        if (textNode.getLength() == t.getStartOffset()) {
          Element sibling=textNode.getParentElement().getNextSiblingElement();
          if ((sibling != null) && (!sibling.getClassName().toLowerCase().contains("String_Node_Str"))) {
            path.set(0,path.get(0) + 1);
            op=new TreeMergeParagraph(clientJupiter.getSiteId(),path.get(0),1,1);
            op.setPath(convertPath(path));
          }
        }
 else {
          op=new TreeDeleteText(clientJupiter.getSiteId(),pos,convertPath(path));
        }
      }
 else       if (Node.ELEMENT_NODE == node.getNodeType()) {
        if (node.getNextSibling() != null) {
          path.set(0,path.get(0) + 1);
          op=new TreeMergeParagraph(clientJupiter.getSiteId(),path.get(0),1,1);
          op.setPath(convertPath(path));
        }
      }
    }
 else     if (keyCode == 13) {
      if (pos == 0 && !isNoteworthyPath(path.subList(1,path.size()))) {
        op=new TreeNewParagraph(clientJupiter.getSiteId(),pos);
        op.setPath(convertPath(path));
      }
 else {
        op=new TreeInsertParagraph(clientJupiter.getSiteId(),pos,convertPath(path));
      }
    }
    if (op != null) {
      clientJupiter.generate(op);
    }
  }
}