Element range index with local name "c" gives XDMP-ELEMRIDXNOTFOUND

I created an Element range index on S, P, C, O (RDF) but C is not working even after reindexing and throwing an error.

XDMP-ELEMRIDXNOTFOUND - No element range index for fn:QName("", "c") http://marklogic.com/collation/codepoint