I used to have the same issue on a customer backup server, even after upgrading to 18.104.22.1680.
After analysing, in my case, VeeamVssSupport Service was running and still running after a reboot of the backuped VM.
Here is what I do to solve my issue :
- I just kill this service
- set startup to manual
- open a cmd as admin
- run : sc delete VeeamVssSupport
- and then finaly restart or retry the job
hope it can help you