The checkbox of "exclude content from site search" ticks again on refresh of page

Hi all,

I linked some item numbers to a subcategory via a multi-reference.
So the idea is that when someone searches on an article number, they will end up on the page of the subcategory.
I put these in a div-block at the top, with a collection list. Already several times I uncheck the ‘exclude from site search’ in the settings of the collection wrapper. But every time I refresh the page, it automatically un-ticks it again and the text is not included in the site search results. Does anyone have an idea why? Is this a bug or am I doing something wrong?

Here is the read-only link.

Did you find a solution? Having the same problem now!