It seems like fseek and fread are causing issues with your PE files, possibly due to buffer problems. Try using fflush(fp) to clear the buffer. The byte 0xda could indicate hidden characters or encoding issues—double-check the raw bytes. Even if PE Bear works fine, certain files might behave differently, so comparing working vs. non-working files could help. Ensure you're handling Windows-specific file quirks, and track the file pointer position to identify where the jump happens.