When dependency contains slash ("/"), Nexus returns 404, although you can install it with bare bower.
Example: package: ckeditor, version: full/4.4.6
package url (returns 404): https://company.registry/repository/bower-public/ckeditor/full/4.4.6/package.tar.gz
version without "full/" prefix (i.e. https://company.registry/repository/bower-public/ckeditor/4.4.6/package.tar.gz) works fine.
Bower repo being proxied: http://registry.bower.io
"Force Bower to retrieve packages through the proxy repository" is checked.