If the file hash is correct, the error is almost certainly hardware-related.
To his surprise, 7-Zip successfully extracted the game's files. Running the executable as an administrator also seemed to do the trick, as the game launched without any issues related to UnArc.dll error code 11.
Error code -11 is almost always related to a failure in the . Unlike other error codes that might signal a missing file, -11 specifically points to: