I have recently taken over a Woocommerce project that uses the WPML plugin from a different studio that created the website for my client. The client reported that the website is very slow at times and some users experience 503 errors.
After looking into the problem by disabling all plugins and enabling them one by one I have concluded that the problem exists when two plugins are active at the same time: Woocommerce and WPML String translation.
Some pages in the admin panel throw 503 errors when I have only these two plugins enabled and the website is considerably slower too.