PHP Warning: array_combine(): Both parameters should have an equal number of elements - CSV not parsing properly?

For the following CSV file (3MB): ACDF_cut.csv

And for the following code:

<?php

$file = fopen("ACDF_cut.csv","r");
$file2 = fopen("ACDF_cut_rounded.csv","w");


    /* Map Rows and Loop Through Them */
    $rows   = array_map('str_getcsv', file('ACDF_cut.csv'));
    $header = array_shift($rows);
    $csv    = array();
    foreach($rows as $row) {
        $csv[] = array_combine($header, $row);
    }



foreach ($csv as &$product){//Use of & as per https://stackoverflow.com/a/40913938/9095603
    $product['LQ Price'] = number_format($product['LQ Price'],2); 
    $product['AvailableQty'] = number_format($product['AvailableQty']); 
    $product['Net Weight'] = number_format($product['Net Weight'],2); 
}


foreach ($csv as $product) {
  fputcsv($file2, $product);
}


 fclose($file);
 fclose($file2);

I get

[03-Jan-2020 17:00:16 UTC] PHP Warning: array_combine(): Both parameters should have an equal number of elements in /home/kalugi/public_html/wp-content/uploads/wpallimport/files/round_ACDF_cut.php on line 20

I can't see how it's possible that $header and $row don't have an equal number of elements.

But indeed on checking I see that:

echo count($header) = 13
echo count($rows) = 8552

Yet they derive from the same non-ragged CSV file where the number of headers matches the number of fields on each row. To make matters more confusing, I've operated on this same file before and never had issues with unequal header and row counts. How do I fix this?