vb-reset-host-version-guestproperty.sh

#!/bin/bash

# Usage: vb-reset-host-version-guestproperty.sh myvmname

VMNAME=$1
VBOXMANAGE="$(which vboxmanage)"

if [ -z "$VMNAME" ]; then
  echo "Must provide name of VM."
  exit 1
fi

# Find UUID
UUID="$($VBOXMANAGE list vms | grep -w $VMNAME | cut -d' ' -f2 | tr -d '{}')"
if [ -z "$UUID" ]; then
  echo "No VM found with the name '$VMNAME'."
  exit 1
fi

echo "Found UUID:$UUID"

# Set latest version
CURRENT_VERSION="$($VBOXMANAGE --version)"
GUESTPROPERTY_VERSION="$($VBOXMANAGE guestproperty get $UUID /VirtualBox/GuestAdd/Version | sed s/Value\:\ //g)"
if [ "$CURRENT_VERSION" != "$GUESTPROPERTY_VERSION" ]; then
  $VBOXMANAGE guestproperty set $UUID /VirtualBox/GuestAdd/Version "$CURRENT_VERSION"
  echo "GuestProperty(/VirtualBox/GuestAdd/Version) updated to '$CURRENT_VERSION' from '$GUESTPROPERTY_VERSION'"
else
  echo "Versions match: $CURRENT_VERSION"
fi

sorry, this does not work for me. sample output for 1 machine (i renamed your script to vbr):

# VBoxManage list vms | grep ycast3
"ycast3_default_1622908794541_20972" {4467a641-fa5b-4dc7-9cc7-6fea666ddbf5}
 # VBoxManage guestproperty get ycast3_default_1622908794541_20972 /VirtualBox/GuestAdd/Version
Value: 6.1.22r144080
 # vbr ycast3_default_1622908794541_20972
Found UUID:4467a641-fa5b-4dc7-9cc7-6fea666ddbf5
Versions match: 6.1.22r144080
 # vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Checking if box 'debian/buster64' version '10.20210409.1' is up to date...
==> default: Clearing any previously set forwarded ports...
==> default: Fixed port collision for 22 => 2222. Now on port 2201.
....
==> default: Machine booted and ready!
Got different reports about installed GuestAdditions version:
Virtualbox on your host claims:   5.2.0
VBoxService inside the vm claims: 6.1.22
Going on, assuming VBoxService is correct...
[default] GuestAdditions seems to be installed (6.1.22) correctly, but not running.
Got different reports about installed GuestAdditions version:
Virtualbox on your host claims:   5.2.0
VBoxService inside the vm claims: 6.1.22
Going on, assuming VBoxService is correct...
Got different reports about installed GuestAdditions version:
Virtualbox on your host claims:   5.2.0
VBoxService inside the vm claims: 6.1.22
Going on, assuming VBoxService is correct...
VirtualBox Guest Additions: Starting.