Athail, adding an "End of branch" should just do that, the lesson should be re-displayed with the End of Branch in place. An End of branch page does not have any content.
There was a missing string in the lesson language file which gives the warning message "No branch table found". This message is shown when you try to add an End of Branch when there is no preceding Branch table in the lesson. That string has just been added to CVS. It's not, however, going to cure your problem. Perhaps getting the latest version of the lesson module might help though.