The problem actually comes from certain third-party plugins calling flush_rewrite_rules(true) function too often. This causes WordPress to overwrite .htaccess. However, in some cases, this happens so often, sometimes even on every page request, that it’s called while browsing the front-end in another language.
When this happens, WPML goes ahead and adds the language folder to home_url as usual. This, however, results with an incorrect RewriteBase in .htaccess and ends up breaking the front-end.
Additionally, you’ll get a 500 Internal Server Error error.
And this is what we’ll see in server logs:
AH00124: Request exceeded the limit of 10 internal redirects due to probable configuration error. Use ‘LimitInternalRecursion’ to increase the limit if necessary. Use ‘LogLevel debug’ to get a backtrace.