ESXi 7.0 blocks all files in a VM even after a snapshot is taken, this includes any previous snapshots. As a result of that, snapshots are skipped by the backup process in ESXi 7.0 and above VMs.
We will probably remove all snapshots previous to backup in some future release, Sysadmins must be aware of this limitation though.
(c)XSIBackup-DC 184.108.40.206 manages this automatically by detecting whether ESXi main version is equal or greater than 7 and deleting all snapshots previous to performing a backup or replica, only if the VM is on.
Please, be aware of this (c)ESXi >= 7 limitation imposed by (c)VMWare design.