Typo3 tx_news extend with custom Fields - Content disappears sometimes, caching Issue?

Question

I'm using Typo3 9.5.5 and I extended the extension tx_news with some custom fields. Everything works fine in front-end and back-end, but sometimes the custom content disappears in front-end and is not shown. Also the debug doesn't show the content. In my opinion it could be a caching problem, because after clearing the complete cache, the custom content is shown again. How can I fix this issue?

I tried to put the needed templates into my custom extension, but the result is the same.

---

<?php

namespace myName\NewsExtend\Domain\Model;

/**
 * News model for default news
 *
 * @package TYPO3
 * @subpackage tx_news
 */
class NewsExtend extends \GeorgRinger\News\Domain\Model\News  {
  /**
   * @var string
   */
 protected $categoryHeader;

 /**
  * @var string
  */
protected $issue;

/**
 * Get categoryHeader
 *
 * @return string
 */
public function getCategoryHeader()
{
    return $this->categoryHeader;
}

/**
 * Set categoryHeader
 *
 * @param string $categoryHeader categoryHeader
 */
public function setCategoryHeader($categoryHeader)
{
    $this->categoryHeader = $categoryHeader;
}

/**
 * Get issue
 *
 * @return string
 */
public function getIssue()
{
    return $this->issue;
}

/**
 * Set issue
 *
 * @param string $issue issue
 */
public function setIssue($issue)
{
    $this->issue = $issue;
}

}

Answer 1

Do you sometimes clear typo3temp which would trigger that as well