Hello CroatiaForEver. Usually the kind of error that you describe occurs when the field codes in your document become corrupted or damaged, though it can also occur if the reference itself is invalid from your library.
What happens if you try to insert this citation into a new, blank document? If the same thing occurs, then you may need to delete and recreate this reference in your library. Running a library repair wouldn’t hurt either, as per http://help.thomson.com/default.asp?portalid=tsc&refid=TS_ENDATABASEFAQ3.
If it works correctly in a new document, try cleaning your document field codes as per http://help.thomson.com/default.asp?portalid=tsc&refid=TS_ENCWYWFAQ15.