Distance search type on an attribute without a Search Distance defined
Matching search type on an attribute without an Attribute Map defined
Substring search type on an attribute without the Search Substring attributes defined

All of these generate invalid SQL query strings which result in 500 Internal Server Error responses with portions of the offending SQL strings attached. May at least want to respond with an "invalid rule" error response instead.

Also: Exact search type works whether attribute has the Exact box checked or not