I've rebooted cdsfs0 to perform the work specified in WP4620.  To wit, available OS patches were applied and the NFS options for rpc.mountd were changed to allow the proper operation of group permissions on /ligo (specifically, --manage-gids was removed from RPCMOUNDOPTS in /etc/defaults/nfs-kernel-server).

NOTE: This means that group permissions should now operate correctly on /ligo should you wish to use them to share files.