What is causing pathauto to generate unwanted text in these URLs?
Pathauto creates the alias when a node is being added or edited, so, if you are using current-page:title it will include the title that Drupal generates for that page, eg, in your case, "Edit Site Article: This is a title", and not just the title of the node.  So I would look into using node:title instead so as to remove any of those potential prefixings.