Woocommerce posts and products links works only once and then get 404 error

Question

Permalink to products and post of my website getting 404 error. after saving the permalink type in Setting -> Permalink page they will work correctly. But if I refresh the links they get 404 error again. Actually the links work only once.

this is my .htaccess file:

<IfModule mod_rewrite.c>
Options +FollowSymLinks
RewriteEngine on
RewriteRule ^.*-(\d+)/$ securityl/index\.php?id=$1&%{QUERY_STRING} [L]
RewriteRule ^.*-y(\d+)/$ securityl/index\.php?cat=$1&%{QUERY_STRING} [L]
RewriteRule ^.*(website[a-z]+map\.xml)$  websiteguide/$1 [L]

RewriteBase /
</IfModule>

I have changed the theme to store front and it's not working.

Answer 1

I realized that some php code changes the content of .htaccess file. The php folder was in a directory named 'securityl'. I've been removed that directory but whenever the website was refreshing the directory and also the php files inside it was recreating. In the end I discovered that some code in wp-include/load.php is creating the directory and I re-downloaded the wordpress and replaced the clean wp-include, then the problem solved and there was no code for creating securityl folder! . I don't know how and why the contents of that files were changed.