Second Insert button not passing ID to insert page properly?

I have a slightly customised results page in that it's a "second level" results page. The first page is www.domainname.com/accountants_results.php. This is a standard DataAssist results page, but on this page I have a link where you can view clients associated with each record, so when you click the link next to the record it passes a variable to the second level results page, i.e. www.domainname.com/clients_results.php?AccountantID=12.

This "second level" results page again is the standard DataAssist results page which has the usual two Insert buttons - one that shows along with the table when there are already records in existence, and one which shows when there are no existing records. I've discovered that although the first one works fine, the second one isn't passing the AccountantID correctly, even though I've copied the button code exactly. It does add the record to the database but it doesn't pass the ID (even though the URL variable seems to be passed to the insert page OK, so the Insert Client button takes you to www.domainname.com/clients_insert.php?AccountantID=12.

Any idea why this Insert button isn't working properly?