Located in the remotejob log for the batch when the data was processed will be the log entry :-
"2013-12-31 23:59:59,999 WARN [common.util.AttachmentUtil] (pool-12-thread-1026:) [#81014] Failed in extracting text from attachment:D:\CW\V90\scratch\temp\esadb\dataStore_case_b1abcde2f9_22329370\attIndexDir\file\1a2b4c4d5e6f1a2b4c4d5e6f1a2b4c4d5e6f\1\1.xlsx :[FileFilter]: unknown error (0x0012) "
This is caused by the metadata of the properties containing a large amount of data, eg. in custom properties.
To resolve and process the item without the error, remove some custom properties/characters from properties page eg. for Excel , Open the spreadsheet, go to (File > Advanced Properties > Custom properties) or (File > Info > Properties > Advanced Properties > Custom tab) and decrease the amount of data stored there. Then re-process the file.