I have the same issue, also NSFW: https://winterfire.itch.io/legacy-of-hestia
The downloads worked fine on the first days, but yesterday i've started receiving reports about corrupted downloads.
I've tried downloading my own game, and it first starts downloading at 20mb/s or more, expected speed for my internet connection, however it eventually drops to 8mb/s, then lower until it finally fails.
It doesn't say "the download has failed" as it would normally happen, but it looks no different than a successfully downloaded game, except for the fact that the size doesn't match up (in my case, only the first 800mb get downloaded). Of course that means the zip will not extract.