Recurring CSS loading error

Hello,

On one of the sites I maintain, I’m encountering the following problem.
Very regularly, the site’s CSS no longer loads for certain pages.
I’m not sure whether WP Fastest Cache is involved, but when I clear the cache, the CSS loads again.
This is a site created with Elementor. The Element Caching setting is deactivated.
Do you have any idea what’s causing the problem?
Thanks