[dazc]

Sounds like point 2 was a negative seo attack. It could be that your /?s page is being cached and getting picked up via crawlers.

You can avaoid this by no caching search pages and applying noindex via X-robots tag https://developers.google.com/search/docs/crawling-indexing/...

[weird-eye-issue]

Cache has nothing to do with this

But yes just noindex search pages like they already said they did

[MobiusHorizons]

I think the question is “how are the behavior of random spammers on your search page getting picked up by the crawler”? The assumption with cache is that searches of one user were being cached so that the crawler saw them. Other alternatives I can imagine are that your search page is powered by google, so it gets the search terms and indexes the results, or that you show popular queries somewhere. But you have to admit that the crawler seeing user generated search terms points to some deeper issue.

[dazc]

Not sure how search result pages can be crawled unless they are cached somewhere?