This is a very similar issue to NPM Server doesn't understand %2F but instead of the / it's the @ that is causing problems. The url that is being used is https://npm.datatables.net/%40datatables.net%2Feditor-dt which I can't control or change. I am hoping that Allan can fix this issue in the verdaccio custom authentication plugin like he did for %2F.
I would open a support ticket, but the person who is the owner of our main account is out of office for a couple of weeks so I can't get access to our support credits.