Navigate to your GTA V installation folder (usually under Program Files\Rockstar Games\Grand Theft Auto V). Locate the file named x64a.rpf. Delete this file or move it to your desktop as a backup.
If you downloaded a 100GB "Extra Quality" repack and are getting this error, the repacker likely included pre-modded archives that are outdated or corrupted. x64arpf failed crc check gta v extra quality