Cause
The Search API adds annotations as it parses queries in order to support round-tripping (search:parse generates an annotated parsed query while search:unparse takes an annotated parsed query and generates a string). The parse/unparse cycle is also used in other areas of the API, including search:remove-constraint. This error indicates that the parsed query cannot be reversed due to missing annotations. It is usually encountered when custom parsing code has been added to extend the API.