The problem is that Microk8s when installed with SNAP it uses the following folder for kubelet with a symlink from /var/lib/kubelet:
/var/snap/microk8s/common/var/lib/kubelet
That together with the very long name of this driver creates a full path to the unix socket:
/var/snap/microk8s/common/var/lib/kubelet/plugins_registry/named-disk.csi.cloud-director.vmware.com-reg.sock
which is 108 bytes long, but the maximum length of a Linux UNIX socket is 107 bytes so kubelet is unable to use this socket.
We resolved the problem changing the root-dir in /var/snap/microk8s/xxxx/args/kubelet
from
--root-dir=${SNAP_COMMON}/var/lib/kubelet
to
--root-dir=/var/lib/kubelet
Many thanks to my colleague Alex for finding the problem.