Function not always working

I have a traffic trading script I made and I have a function to randomly select a trade partners ID from all my active partners that have credits remaining. If there is none then the content is hosted and the user is not sent away and I record that hit as a "Hard Play".

The problem I am having is I have a site that has 700-800 credits and it's ID should be returned more than it is. One of the pages that is set to send users to him is getting no partner ID returned and results in a Hard Play and loss of trade.

Here is the code.

function plug_redirect($base_url,$gameid,$links_credit_limit){

        $sql_query = "SELECT links.linkstatus, links.websiteid, links.credits,
		trade_plugs.gameid,
		trade_plugs.linkid,
		trade_plugs.gamelink
		FROM links, trade_plugs
		WHERE links.linkstatus = 1
		AND links.credits > 0
		AND trade_plugs.gameid = '$gameid'
		AND trade_plugs.gamelink != ''
		AND trade_plugs.linkid=links.websiteid
		ORDER BY rand() LIMIT 1";
        $result = mysql_query($sql_query) or die(mysql_error());
        if(mysql_num_rows($result)) {
			//output as long as there are still available fields
			while($row = mysql_fetch_array($result)) {
				$linkid = $row['websiteid'];
        	}
        } else {
			$linkid = "";
		}

    return $linkid;

}

PHP:

The problem has nothing to do with the trade partner because this is happening to many other pages and partners on my site also. When I run that query in phpMyAdmin it always shows someone but it isn't always doing it on the site.

Does anyone know what is causing this or how to fix it?

 

Sorry to bump but it is extremely important I get this fixed.