Hi,
I have checked your options, and the issue there was not actually the code in this case, but the fact that only the frisomat.nl blog was selected as source on the Multisite options panel: https://i.imgur.com/w8KWVeP.png
I have reset that to default, so the plugin will always use the currently active site only for results.
With this adjustment, and the fix in the code it should work now. The file I have changed previously was:wp-content\plugins\ajax-search-pro\includes\classes\search\class-asp-search-cpt.php
This fix however will be included in the next release.