A Duplicate Content Type has been found Error on using Site Templates

Hi All,

I am assisting a client with moving some site templates between site collections (a production and staging environment).    When i add the site template to the staging site,  it works at first,  but upon modifying the site and re-creating the template, we receive an error indicating that a content type already exists (a duplicate content type has been found).    I have taken the wsp file and opened up the cab to see that there are multiple instances of the content types stored in the ElementsContentType.xml file.    I don't understand why it is creating duplicates in these files when i create the template.   Can anyone shed any light on this?     I have tried deleting the associated lists/content types from the production site, recreating the template, and installing it back over to the test site,  but it still creates duplicates.