ssh under newgrp'ed session fails when using HostbasedAuthentication

Issue

• When using HostbasedAuthentication, performing a ssh command succeeds normally

  $ id
  uid=1000 (myuser) gid=1000(myuser) groups=1000(myuser), 100(users)
  $ ssh remote-system true
  $
  

• When using HostbasedAuthentication, performing a ssh command after changing group using newgrp fails

  $ id
  uid=1000 (myuser) gid=100(users) groups=100(users), 1000(myuser)
  $ newgrp users
  $ ssh remote-system true
  setresgid 1000: Operation not permitted
  ssh_keysign: no reply
  key_sign failed
  $