This might be very simple: after you make any change related to the Source component, I find I have to double-click the green arrow -- showing that metadata does more than just show it -- it updates that metadata, too, based on the source component. Only after that will the Destination component be able to "see" the changes to the Source component.
But if that isn't enough: when making these kind of changes, before I could get them to take effect, I've often had to (1) delete the destination component, (2) delete the destination connection object in SSIS, and (3) delete/rename/move the actual Excel spreadsheet, and then generate a new one by clicking the button (in the Destination component), that generates a new destination file from the metadata.