Symptoms

In WHM console, you see a task in progress that doesn't change its status for an excessively long time. You don't see this activity running in Backup management console, but cannot cancel this task and restarting Acronis Managed Machine service does not cancel it. Other activities run successfully.

Solution

Restart python service:

/usr/local/cpanel/base/3rdparty/acronisbackup/scripts/acronis-backup-srv.sh restart