EDIT: From further investigation I found that derivatives of the above search, "kathleen," "hughson," "hugh" and even "hughes," return the 500 error as well.
I've also encountered this issue. It occurs when you search by one word. Like first or last name only. But when you type full 2 word name it shows the result.
For example... I search "Angel" or "starr" it shows server error 500.
But I search "Angel Starr" then its works fine.
Search issues. I'm sure it's been noticed by now. I thought it was just a specific name.