Changing column headers after load

For many of the tables we load, the column headers are set as a part of the load and all is fine. But, sometimes one or more headers is missed resulting in columns with no header and sometimes a header over the wrong column. I see no way to fix these in the UI. Is there something I am missing? Mostly, it isn't clear why the column header doesn't load. This year it got something like 9 of 11 correctly.