Hi,
I think I managed to fix the problem. There was something wrong with the pagination. When the results were not redirected to the first page (not on /page/1/..) then it was not correct.
I have changed the following options: https://i.imgur.com/gTDAbg1.png
The ordering of the results is not exactly the same, but at least now the same results are returned on the results page. I still don’t know what exactly is conflicting there.