The issue reported below has been reported approximately 2 months ago. Has there been a response?
I am having exactly the same issue.

I have a backup plan in place (Block-level, Real-time backup). Each day I get two emails from MSP. One indicates a successful backup, the other indicates a failure. They arrive within minutes of each other. When I look at the History in MSP, I don't see any indication of a failure.

The failure message says (in part):

ERROR
Terminated Abnormally (code: 1023)
The plan was interrupted abnormally

tab in the MSP 360 application), so I am curious as to what is causing this?