I have no idea if it is you or WP Rocket but when I have both plugins installed (and using also Cloudflare APO cache) then clearing the cache is absolutely INSANE to our server. See attached.
I was not able to find and url requests so most likely this is done by queries to the database. But this is simply not possible to have. We have around 15-20k posts. And we have even preloading disabled in WP Rocket.
When we were clearing the cache or using our site before the CPU was around 50% when clearing the cache. Now, it's just insane and I think it takes around 2 hours to finish.
There are no errors in our error log. A few ones from your logs.
Can you please tell me what's wrong? There is another issue where you request an access so I'll put the info there. But from what I can see, I will give you most likely access to our demo site but the problem doesn't have to be visible there and in every case, I cannot risk having the server overloaded when you test something...
1) Can you please check if the issue still happens when using the WP default theme and only the WPML Plugin and WP Rocket are enabled, and all other plugins disabled.
2) Please check if the issue still happens when WPML is disabled.
3) Can you please check with your hosting or server support what queries are executed and are causing such spikes in the performance. But having that much posts which have preload cache and then clearing them, I think it is kind of expected and probably related to WP Rocket.
Please check my suggestion from above and let me know how it goes.
I will follow it in the future. We have our own server. I don't have time to test everything right now, I would do it on our test server but right now we don't have the time for it. If it will be still there and will be really hard on our server, I'll reopen the ticket. I hope it's possible.