To solve the issue with the VM stun, you can add a registry key on the backup server that will add a delay between the HotAdd detach and the snapshot removal processes. Note that your Veeam Backup & Replication version must be 9.5 Update 3 (220.127.116.116) or later.
To add the registry key, do the following:
The exact value you need can be determined only by testing. In most cases, 60 seconds has been plenty for VMs to detach the disks before the "Snapshot removal" command was issued. Less may also work. It is possible that in some environments a larger delay may be required.