Hi Marko,
The checkbox for caching URI’s with query string is grayed out, so it’s not activated. A search result in this theme does have a query string, for example:
https://www.rustelozebenen.org/?s=ijzer
Yet I still ended up with these weird recursive URI’s containing /search/ in the cache.
I followed your advice, and the problem seems to be solved.
Thanks for your help!