[BUG] npm update does not work with scoped private packages

I'm trying to update a scoped private package using the following command:

npm update @snappykraken/ui-elements

But nothing happens. I can see the following lines in the debug output (--dd):

npm http fetch GET 404 https://registry.npmjs.org/@snappykraken%2fui-elements 2473ms
npm http fetch GET 404 https://registry.npmjs.org/@snappykraken%2fui-elements 1048ms

I guess it should use https://www.npmjs.com/package/@snappykraken/ui-elements instead of https://registry.npmjs.org/@snappykraken%2fui-elements.

Current Behavior:

The latest version of a library doesn't get into node_modules and it is also not changed in package-lock.json.

Expected Behavior:

Both node_modules folder and package-lock.json file should get updated.

Steps To Reproduce:

1. Install a scoped package with npm install
2. Wait until a new version is released (or do it yourself with your own library)
3. Try to update this package with npm update

Environment:

OS: Manjaro Linux (kernel 5.10.23)
Node: v15.11.0
npm: 7.7.5

Start by reproducing the reported npm update @snappykraken/ui-elements flow with a scoped private package and inspect how the npm CLI resolves its registry URL. Compare the result with the expected registry configuration, then verify that both node_modules and package-lock.json update after the package version changes.