[נפתר] After saving new menu entries in another language I have an internal error

Background of the issue:
I am working on a site under development and trying to change the menu entries in another language using WPML. After saving the changes, the .htaccess file is modified as follows: 1) RewriteBase / -> RewriteBase /de/ 2) RewriteRule . /index.php [L] -> RewriteRule . /de/index.php [L]. Reverting these changes resolves the issue.

Symptoms:
After saving new menu entries in another language, I encounter an internal error.

Questions:
What causes the .htaccess file to change when I save menu entries in another language?
How can I prevent the internal error after saving menu changes in another language? This is new, I have no idea what the cause is, do you know this, could it be that it is coming from the latest version of WPML main plugin, any help for further debugging is helpful