Hey there!
Just tested it on two different connections and both files downloaded correctly. There must be something happening with your connection. I used to see this kind of error while downloading in to cases: you've had some quick barely visible disconnections from the net and that disturbed downloading or you've been downloading file for too long and error popped out. Of course I'm not sure if either is happening and I cannot help you here, sorry. :(
Itch.io has a great download speed for it, so I don't think it's their server fault. Maybe try downloading through different browser?