Thank you very much!
I have indentified the issue. The theme tries to get the logo image within a query call, which the search mistakes as the main search query and tries to fix the image. I have put the following code to the functions.php file to remove the image fix code:
add_action('init', 'asp_remove_filters');
function asp_remove_filters() {
WD_ASP_Filters::deregister('wp_get_attachment_image_src', array("EtcFixes", "multisiteImageFix"));
} Keep this code there, this should resolve the problem.