In DefaultLabelManager.java you have

  public int addLabel(ContentEntityObject content, Label label)
    {
...
...
        label.setLastModificationDate(now());
        labelling.setCreationDate(now());
        labelling.setLastModificationDate(now());
...
...
}

There is no need to have label.setLastModificationDate(now()); as this will trigger an update in the labels table to update the modification date. However this information is not used anywhere. Further more it could lead to a deadlock if

two pages are created via templates

Page A, has labelA, labelB and
Page B, has labelB, labelA

If they are created in such a way that the thread A locks labelA and then tries to lock labelB to update however thread B has locked labelB and is waiting to lock LabelA.

This was created from case https://support.atlassian.com/browse/CSP-20472 where I sent them a patch to comment out the line label.setLastModificationDate(now());

Please talk to Matt Ryall about this case, if you need to.