Try umounting multiple times.

roles/lmn_vm/files/pam-umount.sh

@@ -4,25 +4,35 @@
 
 set -eu
 
-LANG=C
 usr="$1"
 uid="$2"
 mtp="$3"
 
-lmuh="/lmn/media/$usr/home"
-lmus="/lmn/media/$usr/share"
+shutdownVMs(){
+    local VMs VM
+    VMs="$(machinectl list --no-legend)"
+    if [[ -n "$VMs" ]] ; then
+	for VM in $VMs ; do
+	    machinectl poweroff "$VM{VM%% *}" || true
+	done
+	sleep 3
+    fi
+    ## Check again:
+    VMs="$(machinectl list --no-legend)"
+    if [[ -n "$VMs" ]] ; then
+	sleep 3
+	for VM in $VMs ; do
+	    machinectl terminate "${VM%% *}" || true
+	done
+    fi
+    #killall -9 virtiofsd
+}
 
-for VMname in $(sudo -u $usr XDG_RUNTIME_DIR="/run/user/$uid" \
-		     virsh list --state-running | grep running | awk '{print $2}'); do
-    sudo -u $usr XDG_RUNTIME_DIR="/run/user/$uid" virsh destroy $VMname || true
-    sleep 1
-done
-#killall -9 virtiofsd
+unbindmnt(){
+    local lmuh="/lmn/media/$usr/home"
+    local lmus="/lmn/media/$usr/share"
+    local N=0 mh=true ms=true
 
-if [[ "$mtp" =~ "/srv/samba/schools" ]] ; then
-    N=0
-    mh=true
-    ms=true
     mountpoint -q $lmuh || mh=false
     mountpoint -q $lmus || ms=false
     while [[ $N -lt 10 ]] && ([[ $mh = true ]] || [[ $ms = true ]]) ; do
@@ -36,5 +46,14 @@ if [[ "$mtp" =~ "/srv/samba/schools" ]] ; then
 	sleep 1
     done
     systemd-cat echo "Tried $N umount(s)."
+}
+
+######################
+
+if [[ "$mtp" =~ "/srv/samba/schools" ]] ; then
+    shutdownVMs
+    unbindmnt
 fi
+
+## Just umount:
 exec umount "$mtp"