Description of problem:

While running backups, some of them are being marked as 'PartiallyFailed', not all of them.
This happens because the openshift-velero-plugin exits with 'status 2' which is seen in the logs of the backup.
Enabling debug in velero to gather more information, we can see a goroutine thread in panic for this plugin

It is believed that this is the culprit of the backup being marked as PartiallyFailed since the plugin crashes due to the panic

Version-Release number of selected component (if applicable):

ROSA OCP cluster
OADP 1.5.3

How reproducible:

Random in customer cluster

Steps to Reproduce:
1. Have multiple schedules that runs at the same time or run multiple backups.
Nothing outside of the ordinary other than the amount of threads enabled in the DPA (itemBlockWorkerCount: 8)

Actual results:

Random backups are marked with 'PartiallyFailed' phase due to openshift-velero-plugin crashing

Expected results:

openshift-velero-plugin should not crash and backup should complete without issues.