We have a really old web application which uses JSP, plain JS and Java 8 running on JBOSS servers and ERR_SSL_PROTOCOL_ERROR randomly occurs whenever application tries to get a resource or make an XHR post request. This error occurs randomly, one minute there is no problem with the request, immediately after that the same request gets the error. If this is a certificate or SSL problem, it would occur all the time. And i can’t see the detail of the error, just ERR_SSL_PROTOCOL_ERR. This application uses iframes. And CORS policy is set to same-origin. So there is no problem with that also. The status of XHR Request is 0 and statusText is empty. How can I get the detail of this error?
By the way we can’t find any log of this request on the server or anywhere else, it is like it’s blocked by the browser somehow. Users access this application from Chrome.

This is my XHR request code:

thisRequestObject.onreadystatechange = processRequest;
function processRequest() {
if (thisRequestObject.readyState == 4) {
    if (thisRequestObject.status == 200) {
        if (callbackFunction)
            callbackFunction(thisRequestObject);
    } else {
        alert("There was an error: (" + thisRequestObject.status + ") " + thisRequestObject.statusText);
    }
}

}

this.sendPostData = function()
{
    if (theURL)
    {
        thisRequestObject.open("POST", theURL, true);
        thisRequestObject.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        thisRequestObject.send(sendString);
    }
};

When this error occurs, i don’t see any response and response headers.

For example;