We disabled one of the admin account on crm 2016, getting user ID belongs to this is disabled error

Hi All,

We have some customization developed on our CRM, to update the contact through other additional form using java scripts updates upon the form save. However no where in this java scripts, we can find the traces of one of the system account (system1) we recently disabled on our environment.

But when we disabled this system account(system1), during the contact update etc, We are facing below error. How to know, what is the reason for this. Is it possible to find this error information further.

example of JS been used is as below.

var entity = {};
entity.subject = "test";
entity["regardingobjectid_contact@odata.bind"] = "/contact(9CFBD4BD-CD4F-E811-A95A-000D3A1A9407)";
entity.responsecode = 3;

var req = newXMLHttpRequest();
req.open("POST", Xrm.Page.context.getClientUrl() + "/api/data/v8.2/contact", true);
req.setRequestHeader("OData-MaxVersion", "4.0");
req.setRequestHeader("OData-Version", "4.0");
req.setRequestHeader("Accept", "application/json");
req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
req.onreadystatechange = function() {
    if (this.readyState === 4) {
        req.onreadystatechange = null;
        if (this.status === 204) {
            var uri = this.getResponseHeader("OData-EntityId");
            var regExp = /\(([^)]+)\)/;
            var matches = regExp.exec(uri);
            var newEntityId = matches[1];
        } else {
            Xrm.Utility.alertDialog(this.statusText);
        }
    }
};
req.send(JSON.stringify(entity));