There is not a solution sadly, I have just put on a text on the dowload page telling the users "The site is experiencing download issues" and to try later if the download fails. Until they fix it on Ich.io side we can't do much else sadly..
Viewing post in .ZIP Files getting corrupted on download
Ah well, I'm sure they're working on it. I was looking around more though, even though my download is free,I was able to get the "Downloads not starting?" button to work. I'm not sure if it's because I have a second optional file you can download, (it's a .txt file with credits for the assets I used), but it seemed to work for me for now!