I found another one of these case items:
This one on the backend, when viewing a user just after the search, then going to "View Details", that link is looking for ".... /admin/users_Detail.php" rather than the extant ".... /admin/users_detail.php".
I'll keep this going here as I find more.
Rather than going in and correcting it, I renamed a copy of the file to cover all the bases. Shouldn't matter, should it?