Hostgator are incorrect. I occasionally chat to them via email or in person so I'll bring this up next time we chat.
Wordfence calls admin-ajax.php when it runs a scan or when you're viewing live traffic to update your view. Those are the only times admin-ajax.php is called. So it sounds like your site got into a scanning loop.
It sounds like misconfiguration is causing it to repeatedly scan. So I'd recommend either removing WF or unchecking the box on the options page to "Enable automatic scheduled scans" and Save which will disable scheduled scans.
Regards,
Mark.