Not WPML issue

Problem:
The client is experiencing an issue where the language parameter is being added to the .htaccess file on multiple sites using WPML, causing the website to become unusable. The altered .htaccess file includes a language base such as /en/, /ru/, or /lt/ which disrupts the site's functionality.
Solution:
If you're encountering this issue, we recommend following the workaround provided in the WPML documentation. Please visit the following link for a detailed guide and explanation of the root cause: https://wpml.org/faq/why-is-htaccess-getting-overwritten-with-the-language-folder-on-my-wpml-website/.

Please note that this solution might be outdated or not applicable to your specific case. We highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If the issue persists, please open a new support ticket for further assistance.

Problem:
You are trying to open a page to translate using WPML and encounter a fatal error:

Uncaught Error: Call to undefined function mb_ereg_replace_callback()

.
Solution:
We recommend installing the Multibyte String extension on your server as it appears to be missing, specifically the

mb_ereg_replace_callback

function. This should resolve the fatal error you are experiencing. Additionally, ensure that your server meets all the minimum requirements for running WPML, which you can check here: WPML Minimum Requirements.

If this solution does not apply to your case, or if it seems outdated, we highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. Should you need further assistance, please do not hesitate to open a new support ticket at WPML Support Forum.