Magento 2 , preference in di.xml is not working il all places in admin panel

Question

I am trying to rewrite the behavior of the method: "render" in the class: "vendor/magento/module-config/Block/System/Config/Form/Field.php"

This is my di.xml file:

<?xml version="1.0"?>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="Magento\Config\Block\System\Config\Form\Field" type="Cnnb\GeneralFixes\Block\System\Config\Form\Field"/>
</config>

this is the my new class "Field.php"

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

namespace Cnnb\GeneralFixes\Block\System\Config\Form;

use Magento\Framework\App\ObjectManager;
use Magento\Backend\Block\Template\Context;
use Magento\Framework\View\Helper\SecureHtmlRenderer;

/**
 * Render field html element in Stores Configuration
 *
 * @api
 * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
 * @SuppressWarnings(PHPMD.NumberOfChildren)
 * @since 100.0.2
 */
class Field extends \Magento\Config\Block\System\Config\Form\Field
{
    /**
     * @var SecureHtmlRenderer
     */
    private $secureRenderer;

    /**
     * @param Context $context
     * @param array $data
     * @param SecureHtmlRenderer|null $secureRenderer
     */
    public function __construct(
        Context $context,
        array $data = [],
        ?SecureHtmlRenderer $secureRenderer = null
    ) {
        parent::__construct($context, $data, $secureRenderer);
    }

    protected function _renderInheritCheckboxFix(\Magento\Framework\Data\Form\Element\AbstractElement $element)
    {
        $htmlId = $element->getHtmlId();
        $namePrefix = preg_replace('#\[value\](\[\])?$#', '', $element->getName());
        $checkedHtml = $element->getInherit() == 1 ? 'checked="checked"' : '';
        $disabled = $element->getIsDisableInheritance() == true ? ' disabled="disabled" readonly="1"' : '';

        $html = '<td class="use-default">';
        $html .= '<input id="' .
            $htmlId .
            '_inherit" name="' .
            $namePrefix .
            '[inherit]" type="checkbox" value="1"' .
            ' class="checkbox config-inherit" ' .
            $checkedHtml . $disabled .
            ' />';

        if(!(is_null($this->secureRenderer)))
        {
            $html .= /* @noEscape */ $this->secureRenderer->renderEventListenerAsTag(
                    'onclick',
                    "toggleValueElements(this, Element.previous(this.parentNode))",
                    'input#' . $htmlId . '_inherit'
                );
        }
        
        $html .= '<label for="' . $htmlId . '_inherit" class="inherit">' . $this->_getInheritCheckboxLabel(
            $element
        ) . '</label>';
        $html .= '</td>';

        return $html;
    }

    /**
     * Retrieve HTML markup for given form element
     *
     * @param \Magento\Framework\Data\Form\Element\AbstractElement $element
     * @return string
     */
    public function render(\Magento\Framework\Data\Form\Element\AbstractElement $element)
    {
        echo __FILE__."<br>";

        $isCheckboxRequired = $this->_isInheritCheckboxRequired($element);

        // Disable element if value is inherited from other scope. Flag has to be set before the value is rendered.
        if ($element->getInherit() == 1 && $isCheckboxRequired) {
            $element->setDisabled(true);
        }

        if ($element->getIsDisableInheritance()) {
            $element->setReadonly(true);
        }

        $html = '<td class="label"><label for="' .
            $element->getHtmlId() . '"><span' .
            $this->_renderScopeLabel($element) . '>' .
            $element->getLabel() .
            '</span></label></td>';
        $html .= $this->_renderValue($element);

        if ($isCheckboxRequired) {
            $html .= $this->_renderInheritCheckboxFix($element);
        }

        $html .= $this->_renderHint($element);

        return $this->_decorateRowHtml($element, $html);
    }




}

in the admin panel (especially in the option: configuration-->sales-->payments), i can see the name of my new class , but not always !!! i see also the behavior of the old class !!!! so my preference in di.xml is not working all the times !!!

Why ??