So, in the excel source, in the advanced editor, it probably shows a mismatch between the actual column size (which isn't shown anywhere), the external column size and the output column size. Truncation will occur, and the task will stop, when it tries to move the external column to the output column. If you right click on the task and bring up the advanced editor, you can change the column lengths for those 2 entries and that may take care of the problem.

If you can run the package in debug mode, you'll probably get better error messages.