URL rewriting can be the source of suffering unless you are very careful in applying the rules.
My English version of the site has been only accessible at the front page only for the last few days due to the error in the file .htaccess.
% diff ./en/.htaccess ./ja/.htaccess 21c21 < RewriteBase /spinorlab.matrix.jp/en/ --- > RewriteBase /ja/ 25c25 < RewriteRule . /spinorlab.matrix.jp/en/index.php [L] --- > RewriteRule . /ja/index.php [L]
I suppose the error is introduced by the plugin I was trying to use to move my English site to HTTPS.