$.ajax is not working inside setInterval

I'm expecting $.ajax to work inside setInterval callback

1.3.15

Having updates on the issue.
$.ajax is configured by default to send POST:

   $.ajaxSetup({
        type: 'POST',
    });

But inside setInterval it sends GET.
And if I specify POST directly in $.ajax then it won't work at all:

    $.ajax({
        type: 'POST',
        url: '/my/url',
    });