Antivirus software (Windows Defender, Avast, etc.) sometimes blocks the unarcdll from reading the compressed game files, assuming they are malicious.
Corrupt system libraries can occasionally cause unarc errors. unarcdll error code 12 dodi repack
Error 12 can appear if your system runs out of memory during decompression. Antivirus software (Windows Defender, Avast, etc
Sometimes the hard drive you are extracting from or to has bad sectors or permission issues. Antivirus software (Windows Defender
If your C: drive is an SSD with less than 15% free space or if Windows User Account Control (UAC) is interfering, the installer may fail to write temporary files, triggering Code 12.
How to do it: