TYPO3 Core

Hi community.

The issue is quite weird and it is a combination of multiple factors. Let's go step by step.
Website menu links are generated via <f:link.page pageUid="{mainMenuItem.uid}">{mainMenuItem.linktext}</f:link.page> and since f.link.page by default uses cHash, the links look like http://domain.tld/index.php?id=11&L=0&cHash=82665c06c7bb6aebebc536bd4da96382

Not critical and with RealURL the path still looks nice, e.g. domain.tld/about-us/

But if somewhere else a link to a same page is generated without cHash, the page is duplicated in index:

And then if I search for some words, that are available on such a page it might appear twice:
First like a normal links with cHash:
http://domain.tld/index.php?id=11&L=0&cHash=82665c06c7bb6aebebc536bd4da96382

And second time as the same link but with duplicated id:
http://domain.tld/index.php?id=11&L=0&id=11&cHash=82665c06c7bb6aebebc536bd4da96382

The main problem is, that I can't reproduce duplicated search results in my development environment (although duplicated indexing results and result link with double-id are still reproducible), but it is a case on a production server.

As a poor-man's fix, one can force noCacheHash for page links, but it seems ugly and still no guarantee, that link with cHash can be generated in some other part of the website.

The main question here: is it broken indexing, which indexes same page twice or is search, which duplicates the 'id' parameter? Or both?

TYPO3 8.7.3