Well wordpress in general does not allow anything else than posts and other post types as results.
The search tries to “trick” wordpress by pushing a fake post instead of the users, and then correcting the titles and the URLs later – but unfortunately in many cases it won’t work, as it’s not supposed to work in the first place.
The only way to maybe have those results is by editing the search results template file in the theme directory and integrating the ajax search pro theme functions to get the original result titles, images, excerpts and urls. It is still possible that these won’t work, strongly depends if the query persists the data sent by the search.