When processing certain documents with an OCR format configured to use the Most accurate Recognizer setting, older versions of the Hyland OCR Engine may encode some difficult-to-read pixels as invalid ASCII characters and leave the text renditions of these documents incomplete.
If you are using an OCR format that is configured to use the Windows ANSI code page and either the ASCII Text (Standard) or ASCII Text (Formatted) output format, reprocessing these documents often resolves the issue. If you must use a different OCR format configuration, upgrading to the most recent version of the Hyland OCR Engine resolves the issue.