I had the same problem at around 28%, I tried all advice here, so I reinstalled the launcher.
Now even the launcher fails to download its update, so I can’t even select 4.1 for download anymore…
Chunks 43CA8A014D930326C860829D1737A0E9 and 5B323DD945241A8146E6D4AC2E84927B fail to download over and over again until it gives up.