I have the same issue, downloading from the website, the file is corrupt every time. When downloading through the app it gets to a point where it is almost complete and then restarts the download over and over again
This is an issue with the Itch.io website: https://itch.io/t/3306553/download-file-corruption-reports
If you email our support email vimstudios.vns@gmail.com with the email you used to purchase the game on Itch (so we can verify purchase), we can send you an alternative download link. Sorry about the inconvenience