The error redirect output is empty with only column headers

I have a task which performs the following:

1. read data from a text file (source) - (id, zipcode)

2. match/lookup a zip code column against a SQL table (source) - (zipcode, city, state)

3. populate the matched result to another SQL table (destination) - (id, city, state, zipcode)

for the unmatched (which would cause error), I output an error redirect text file.

Before I used the "error redirect" option, I ran the task with the"Ignore Error" option and I can see the unmatched records in the destination SQL table that look similar in the following fashion:

idcitystatezipcode

.........

2NULLNULL12345

Then when I ran the task with the "Ignore Error" option, I can see the matched records in the destination SQL table, but only column headers in the error redirect text file.  

I checked the Execution Results,  I can see 

[SSIS.Pipeline] Information: "component "OLE DB Destination" (57)" wrote 4 rows.
[SSIS.Pipeline] Information: "component "Flat File Destination" (115)" wrote 1 rows.

The later one is the error redirect output file.  It shows that one row got written to it.

Why the error redirect output file is empty with only the column header?

Could anyone help?

BI Analyst