Blank Woocommerce Shop Page | WordPress.org

Hi,

I have a problem with wordpress and woocommerce.
Every now and then it happens that the shop page in woocommerce comes up empty. I found that this is due to the fact that the rewrite_rules record in wp_options is missing the shop rewrite rules.
It doesn’t happen often but I can never replicate this problem. It has happened to me on several sites with different themes and plugins.
I don’t understand how this can happen, but if I rewrite the permalinks the problem goes away.
How is it possible that $wp_rewrite->flush_rules(); fails to generate the links for woocommerce shop?
Thanks