I had a little bit different scenario but I believe this should also work in your case:

At the installation folder where vs_community.exe resides, theres a folder Win10SDK_{version}. Click on it and choose winsdksetup.exe. I did it while the installer was open. When winsdksetup.exe finished, kill the installer via TaskManager, and start it again (I didn't restart my computer), the installation finished successfuly (after being stuck a little while on Microsot.Net.Core).