Using plink.exe to run commands on AnywhereUSB14

We have multiple Digi AnywhereBCS/14 devices. We want to make regular config backups of these devices. And we want to schedule it via script.
There is CLI command for it: backup to=:digibackup.cfg passwords
I’ve tried to use plink.exe for executing this command via ssh:
plink --v IP -l admin -pw “backup to=:digibackup.cfg passwords”.
But somehow after successful authentication plink.exe enters interactive shell/command mode and doesn’t executes command automatically. Usually plink.exe works well with any devices that support ssh.
Maybe something wrong with ssh in AnywhereBCS/14?
Or is there another way to make regual automated backups of Digi configs?

webpage of plink/putty:
Our firmware is (build 82002081_H awusb14 eos 9/17/2013 10:29:44a)

contact Digi Technical support.

When we bought that Digi, support was included. Now as I see to contact technical support we have to buy support additionally.
Actually for now we pipe commands for digi to plink from another cmd file. It works.