I've been reading about this issue, and there are many posts on the internet reporting this problem with itch.io.
It seems that depending on the time, browser, or location, itch.io experiences instability and ends up showing that the file was downloaded correctly when in fact several parts of it are missing. I imagine it's because of the volume of downloads they manage.
When this happens, check the game's page on Patreon (link below). As some have already commented on this issue, I have provided an alternative download link using Google Drive.
The download post is public, so you don't need to be a Patreon member to access it.
Look for the post referring to release 9.1