Indicates entries have the same reader+fieldname but different cached values. this can happen if different datatypes, or parsers are used -- and while it's not necessarily a bug it's typically an indication of a possible problem.
NOTE: Only the reader, fieldname, and cached value are actually tested -- if two cache entries have different parsers or datatypes but the cached values are the same Object (== not just equal()) this method does not consider that a red flag. this allows for subtle variations in the way a Parser is specified (null vs DEFAULT_LONG_PARSER, etc...)