Entering characters as a value only provides entries in the drop-down menu for the search scheme "starts with" instead of "contains".

Example:
Entering "John" as a value for a custom field only shows values such as "John Smith" or "John Doe" in the drop-down menu ("John" appears at the beginning of the value). It does not return values like "James John Doe" or "Doe, John" ("John" does not appear at the beginning of the value).

There should be a mechanism to switch the search behavior of the on-the-fly search in order to deliver better results.