If you are on a server running cPanel 11.38 or later, then all cronjobs on that server run inder jailshell by default, which appears to affect the way PHP runs when called from a user's crontab. That being said, you can try the following:
ORIGINAL:
php /path/to/cart/admin.php --dispatch=exim.cron_export --cron_password=GshdFYJH
NEW:
lynx --dump --accept_all_cookies "https://www.yourdomain/admin.php?dispatch=exim.cron_export&cron_password=MYPASS"
