cache bypassed, preload feature issue ?

Hello,
I have created a website with Elementor and lot of dynamic content. The generation of a page without caching take some times. A page (detail page) is composed by several different posts). To reduce this time we use WP Super Cache which does a great job by generating the corresponding static page.

The problem we are facing is that the first access seems to bee always slow even when the preload feature has done its job. It seems that the cache content is created when we access a page for the first time then the content is displayed at light speed. Sometimes when we access the same page again, for an unknown reason the access is again slow and it seems that the page is not coming from the cache or the cache is bypassed; as it is recreated dynamically.

I am using also the preload feature. It seems that the preload resets the cached page which in fact is normal, but I am wondering why the first access is slow even after the reload ?

I probably do something wrong somewhere …

I will greatly appreciate some help to figure out what we can do to solve this issue.

Thanks for any help.

Best regards.

John