Form validation callbacks not working

Hello,

After upgrade from 2.2.6 to 3.1.9. I noticed my callback function for form validation not working.

PHP Code:

function update_password()
    {
        
        if($this->session->userdata('recovery')!='yes')
        $this->form_validation->set_rules('current_password', 'Current Password', 'callback_currentpass_check');
        
        $this->form_validation->set_rules('new_password', 'New Password', 'required|matches[re_password]');
        $this->form_validation->set_rules('re_password', 'Password Confirmation', 'required');
            
        if ($this->form_validation->run() == FALSE)
        {
            $this->changepass();    
        }
        else
        {
            
                $password = $this->input->post('new_password');
                $this->auth_model->update_password($password);
                $this->session->set_userdata('recovery',"no");
                $this->session->set_flashdata('msg', '<div class="alert alert-success">Password changed successfully</div>');                
            
            redirect(site_url('admin/auth/changepass'));        
        }
    
    } 


PHP Code:

public function currentpass_check($str)
    {
        $user_name = 'test_user';
        $res = $this->auth_model->check_login($user_name,$str);
        
        if ($res == 0)
        {
            $this->form_validation->set_message('currentpass_check', 'Current password Didn\'t match');
            return FALSE;
        }
        else
        {
            return TRUE;
            
        }
    } 


I am getting this error.

My callback function ( currentpass_check) returns TRUE.

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