qemu-monitor-event command gets stuck randomly

We are using kvm virtualization on our servers, We use "qemu-monitor-command"(drive-backup) to take qcow2 backups and to monitor them we use "qemu-monitor-event" command 
For eg:-
/usr/bin/virsh qemu-monitor-event VPSNAME --event "BLOCK_JOB_COMPLETED\|BLOCK_JOB_ERROR" --regex

the above command stucks randomly (backup completes but still it is waiting) and because of which other vms backup are stucked until we kill that process.

Can you suggest how can we debug this further to find the actual issue.


/usr/bin/virsh version

Compiled against library: libvirt 4.5.0
Using library: libvirt 4.5.0
Using API: QEMU 4.5.0
Running hypervisor: QEMU 2.0.0

cat /etc/os-release
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"