AspNet on Kestrel server stress test failure

Hi,

im testing of very simple Web API application running on Kestrel server.

Application does simple xml read/parse and return an object (json/xml).
A test client application(siege) does a series of calls with number of users. For some reason test stuck as no responses coming frm the app (having placed url into the browser while test is in stuck i get responses...).

I build a test console app to do the same and found every time 3rd call hangs and requests go to timeouts.

A call URL is build with custom attribute to avoid reading frm cache:

http://url:5000/some/path?n=1
http://url:5000/some/path?n=2
.....
http://url:5000/some/path?n=100

Any idea?

Same test pass when i try it with IISExpress.

EDIT: I changed a method to be as simple as:

        public string Test1()
        {
            return "Test";
}

Its still refuses to send responses after 2nd request...