`fields cannot be identical: ' ' and ' '` mongoimport error

Question

i'm trying to import a csv into mongodb on my local machine. I used the following commmand from the shell:

mongoimport -d mydb -c things --type csv --file /Users/..../agentsFullOutput.csv --headerline

I get the following error:

Failed: fields cannot be identical: '' and ''

I can't find anything on what that means. What am I doing wrong? The csv file, by the way, is the result of a mongoexport.

here are the column headers and some data:

_id build_profile   company_address company_name    company_website created_at  device _token   downloaded_app  email   first_name  last_name   is_proapp   modified_at mobile_phone    terms_accepted_at   license_number  broker_id   join_unique_url linkedin_profile_id billing_customer_id billing_zip mobile_phone    office_phone    vendors_count   clients_count   app_client
ObjectID(52ab245b763f4aec448b6763)  0   California  Lateral test    2014-01-01T08:19:05.470Z            test    test    test        2015-04-18T05:16:37.155Z    (123) 123-1234                          zip (123) 123-1234      10  5   
ObjectID(52b46bfc763f4ad9198b45ab)      7928    test    test    2014-01-01T08:19:05.470Z                Jennifer    Chase       2015-04-15T17:05:17.114Z            5551112     jennifer-chase      test    7071            22  64