Login Not happening Correctly in Codeignitor 3.1.11 php 7.4

When I click on Login button, 1) then login successfully message appears. 2) I also checked session is created successfully as I put response line $resp = array('status'=>'1','msg'=>$this->lang->line('ltr_logged_msg'),'url'=>$url); inside condition if ($this->session->has_userdata('email')), it shows session is also created. 3) I also checked overall code and debug the code in browser also. I cannot find out any reason why it comes back to the login page. That’s why I am here for your assistance. I attached relevent View file code, Controller code as well as js file code so that anyone can test it. Looking forward to your guideance

Issue that I traced till now is related to session:
at location.href = resp.url; when I provided the url that is not linked to the session, it goes to that url immediately. When I put this admin/bashboard with base url. Then it comes back. Why session is destorying, I cannot find the reason till now.

Session Settings in Config.php file

$config['sess_driver'] = 'files';
$config['sess_cookie_name'] = 'ci_session_alhuda';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = BASEPATH . '/cache/';
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 300;
$config['sess_regenerate_destroy'] = FALSE;

In view Login.php

<form class="form" method="post" action="<?php echo base_url().'front_ajax/login'; ?>" data-redirect="yes">
    <div class="edu_field_holder">
        <input type="text" class="edu_form_field require" name="email" placeholder="<?php echo html_escape($this->common->languageTranslator('ltr_p_email'));?>" autocomplete="off" value="<?php echo(isset($_COOKIE['UML'])) ? base64_decode(urldecode(base64_decode($_COOKIE['UML']))) : ''; ?>">
    </div>
    <div class="edu_field_holder">
        <input type="password" name="password" class="require edu_form_field" placeholder="<?php echo html_escape($this->common->languageTranslator('ltr_password'));?>" value="<?php echo(isset($_COOKIE['SSD'])) ? base64_decode(urldecode(base64_decode($_COOKIE['SSD']))) : ''; ?>">
    </div>
    
    <div class="col-lg-6 col-md-6 col-sm-12 col-12 text-md-right">
        <button class="edu_btn edu_btn_black" id="auth_login" type="button" data-action="submitThisForm"><?php echo html_escape($this->common->languageTranslator('ltr_login'));?></button>
    </div>      
</form>

In Controller Front_ajax.php

function login(){
    if(isset($_SERVER['HTTP_X_REQUESTED_WITH']) && ($_SERVER['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest')){
        if(!empty($this->input->post('email',false)) && !empty($this->input->post('password',false))){          
            $email = trim($this->input->post('email',TRUE));
            $pass = md5(trim($this->input->post('password',TRUE)));     
            if(!filter_var($email, FILTER_VALIDATE_EMAIL)){
                $stud_cond = array('enrollment_id'=>$email,'password'=>$pass);
            }else{
                $stud_cond = array('email'=>$email,'password'=>$pass);
            }
            $userDetails = $this->db_model->select_data('id,name,role,status,parent_id,teach_image,email,teach_batch,teach_subject,super_admin','users use index (id)',array('email'=>$email,'password'=>$pass),1);
            $studentDetails = $this->db_model->select_data('id,name,contact_no,batch_id,admin_id,enrollment_id,image,email,status,login_status','students use index (id)',$stud_cond,1);          
            $this->session->sess_destroy();
            if(!empty($userDetails)){
                  if($userDetails[0]['status']=='1'){
                    $brewers_strings = $this->random_strings(10);
                    $sess_arr = array(
                                'uid'=> $userDetails[0]['id'],
                                'name'=> $userDetails[0]['name'],
                                'role'=> $userDetails[0]['role'],
                                'status'=> $userDetails[0]['status'],
                                'admin_id' => $userDetails[0]['parent_id'],
                                'profile_img' => $userDetails[0]['teach_image'],
                                'email' => $userDetails[0]['email'],
                                'mobile' => $userDetails[0]['contact_no'],
                                'brewers_check' => $brewers_strings,
                                'super_admin' => $userDetails[0]['super_admin'],
                               
                            );
                        
                    $url = '';
                        $url = base_url().'admin/dashboard';
                                            
                    $this->session->set_userdata($sess_arr);
                        
                    $resp = array('status'=>'1','msg'=>$this->lang->line('ltr_logged_msg'),'url'=>$url);//
                    
                    $this->db_model->update_data_limit('users use index (id)',$this->security->xss_clean(array('token'=>1,'brewers_check'=>$brewers_strings)),array('id'=>$userDetails[0]['id']),1);
                  }else{
                    $resp = array('status' => '0','msg' =>$this->lang->line('ltr_contact_to_admin_msg'));//
                }
            }
            else{
                $resp = array('status' => '0','msg' =>$this->lang->line('ltr_wrong_credentials_msg'));
            }
        }
        else{
            $resp = array('status' => '0','msg' =>$this->lang->line('ltr_wrong_credentials_msg'));
        }
        echo json_encode($resp,JSON_UNESCAPED_SLASHES);
    }
    else{
        echo $this->lang->line('ltr_not_allowed_msg');
    } 
}

In login.js

$(document).ready(function(){
$('[data-action="submitThisForm"]').on('click' , function(){
    var targetForm = $(this).closest('form');
    if(!myCustom.checkFormFields(targetForm)){
        myCustom.callFormAjax(targetForm).done(function(res){
            var resp = $.parseJSON(res);
            if(resp.status == 1){
                if(typeof targetForm.attr('data-reset') != 'undefined' && targetForm.attr('data-reset') == 1){ //check reset form data
                    targetForm[0].reset();
                }
                if(typeof targetForm.attr('data-redirect') != 'undefined'){ //check reset form data
                    if(resp.msg != '')
                        toastr.success(resp.msg)
                    setTimeout(function(){
                        location.href = resp.url;   
                    },1500)
                }else if(resp.msg){
                    toastr.success(resp.msg);
                }
            }else if(resp.status == 2){
                $.magnificPopup.open({
                    items: {
                        src: '#studentLogin',
                    },
                    type: 'inline'
                });
                $('#studentLogin .changeStudentLogin').attr('data-id',resp.student_id);
            }
            else if(resp.status == 0){
                toastr.error((resp.msg)?resp.msg:resp.error);
            }
        });
    }
});