If a temp table already exists in the DB, the upgrade manager gives an command prompt error "Error : Please wait reverting to old build!!!" and also notes in the UI that it is unable to overwrite a specific table
In my case the offending table was. "POStatusHistory_TEMP"
As a work around I renamed the table to "POStatusHistory_TEMP_old" and after restarting the upgrade the upgrade manager progressed along successfully.