I am surprised that no one has noticed this. The search via the form is always limited to a maximum of 10 results. Go for example on "Group" and just type a letter in "description" OR select all categories, the result found is invariably 10 maximum.
The problem is the same for the Member search form. I found it because I used "Dolphin Migration" and at first I thought the problem came from him.
I tried here, it's the same problem. Maybe something is missing to go to the next page?