Hi Dirk,
I once saw an issue which is related to the proxy server due to a network configuration of the machine.
Several things you may want to test:
set the proxy variables in a bash environment (on the machine running XSA) and run:
curl <url of the npm module in registry.npmjs.org>
If you are able to run the curl command then maybe the problem is with the NO_PROXY variable.
Make sure the value of the NO_PROXY command is the result of running:
hostname
and:
hostname -f
If that doesn't work I guess a support ticket is in order.
Hope this helps.
Regards,
Omer.