There is the other thread where the problem was officially said to be with the new hosting services itch uses. They pushed a hotfix, but it does not seem to have fixed the issue, yet.
There are reports from USA, Europe, Asia for those corrupted files.
It also seems to be chance based. With small sample size you can get any tendency. Someone posted it happened for a 15MB file. Others have downloads being silently stopped above 2GB.
Also, depending on how the archive was compressed, you can install a game, and the missing files won't affect the game for some time - or you can't even decompress. This is quite normal for this type of error, but we are not used to this kind of error. It should not happen, not silently. Normally the browser would tell you, that the download failed. And on the tcp/ip protocol there should not be any mishaps to begin with.
Timeouts, connection resets and the like maybe. But not this. I would guess they screwed up some load balancing or other obscure things. One server thinking the other server handles the transfer, while being in the middle of one, or other occult shenanigans.