Npm version 7.2 - snapshot v21 rc4 - error Ebusy

I successfully build nodejs and install npm for openwrt snapshot v21 rc4, chipset BCM2711 (raspberry pi 4)
Node works fine but npm does not.
for each package I would like to install, using "npm install command"
it throws out this error:

npm ERR! code EBUSY
npm ERR! syscall getaddrinfo
npm ERR! errno EBUSY
npm ERR! request to failed, reason: getaddrinfo EBUSY

I googled a lot by searching inside node forums too and I tried almost everything:

  • npm config set
  • npm cache-clean
  • updating npm to v7.21 lts
  • put inside /etc/hosts
  • rebooting
  • changed permissions to 755 for all the files inside /usr/lib/node_modules/npm
  • changed internet connection
  • changed dns servers using static ip addresses (both google and opendns)
  • no proxy used

Is there anyone that uses npm without issues?
What cause can produce this problem?