This issue occurs when the search query contains a wildcard character. An example of a search query for which you experience this issue is as follows.
select contents from scope() where WITH
("DAV:contentclass":0,"urn:schemas.microsoft.com:fulltextqueryinfo:description":0,"urn:schemas.microsoft.
com:fulltextqueryinfo:sourcegroup":0,"urn:schemas.microsoft.com:fulltextqueryinfo:cataloggroup":0,"urn:schemas
-microsoft-com:office:office#Keywords":1.0,"urn:schemas-microsoft-
com:office:office#Title":0.9,"DAV:displayname":0.9,"urn:schemas-microsoft-
com:publishing:Category":0.8,"urn:schemas-microsoft-com:office:office#Subject":0.8,"urn:schemas-microsoft-
com:office:office#Author":0.7,"urn:schemas-microsoft-com:office:office#Description":0.5,"urn:schemas-microsoft-
com:sharepoint:portal:profile:PreferredName":0.2,"urn:schemas-microsoft-
com:publishing:HomeBestBetKeywords":0.0,contents:0.1,*:0.05) AS #WeightedProps ..(("urn:schemas-microsoft-
com:publishing:HomeBestBetKeywords"= some array ['microsoft'] RANK BY COERCION(absolute, 999))..OR (FREETEXT
("urn:schemas-microsoft-com:sharepoint:portal:profile:PreferredName", 'microsoft') RANK BY COERCION(multiply,
0.01))..OR FREETEXT(#WeightedProps, 'microsoft') ....OR CONTAINS("urn:schemas-microsoft-
com:sharepoint:portal:profile:PreferredName", '"microsoft"') RANK BY COERCION(multiply, 0.01)..
OR CONTAINS(#WeightedProps, '"microsoft"')..).... AND (("PKMEvent"='ADD') OR ("PKMEvent"='MODIFY'))"CONTAINS
(#WeightedProps, '"microsoft"')..).... AND (("PKMEvent"='ADD') OR ("PKMEvent"='MODIFY'))"
property.