[Resolved] Error 404 when WPML String Translation, WPML Woocommerce and CMS Nav is active

Background of the issue:
When I activate the WPML String Translation and WPML Woocommerce Multilingual plugins on my site hidden link, I get a 404 error when trying to access all pages except for the homepage. For example, when the plugins are not active, I can access the About Us page in both Turkish and English without any issues. However, when I activate them, I can't access either of them. I can only access the homepage. When I check with WP_DEBUG, I see the following error: Warning: preg_replace(): Unknown modifier 'f' in /home/u427736266/domains/derminix.com.tr/public_html/wp-content/plugins/sitepress-multilingual-cms/classes/url-handling/class-wpml-endpoints-support.php on line 142

Symptoms:
404 error when trying to access all pages except for the homepage after activating WPML String Translation and WPML Woocommerce Multilingual plugins. WP_DEBUG shows: Warning: preg_replace(): Unknown modifier 'f' in /home/u427736266/domains/derminix.com.tr/public_html/wp-content/plugins/sitepress-multilingual-cms/classes/url-handling/class-wpml-endpoints-support.php on line 142

Questions:
How can I resolve the 404 error when WPML String Translation and WPML Woocommerce Multilingual plugins are active?
What does the WP_DEBUG error message mean and how can I fix it?