Jenkins Helm backup fails with WebIdentityErr

Question

I have Jenkins running in an AWS EKS cluster. It was deployed using the helm chart available at jenkinsci/jenkins. I want to use the backup option that is included in the helm chart. My configuration for backup looks like:

backup:
  enabled: true
  schedule: "* 04 * * *"
  annotations:
    eks.amazonaws.com/role-arn: "arn:aws:iam::221100446688:role/jenkins-backup"
  image:
    repository: "maorfr/kube-tasks"
    tag: "0.2.0"
  destination: "s3://my-jenkins-tings/backup"

I'm getting this error:

2020/09/27 05:08:56 Backup started!
2020/09/27 05:08:56 Getting clients
2020/09/27 05:08:59 WebIdentityErr: unable to read file at /var/run/secrets/eks.amazonaws.com/serviceaccount/token
caused by: open /var/run/secrets/eks.amazonaws.com/serviceaccount/token: permission denied

I have tried adding fsUser & Group, even updating the annotation for the jenkins-backup service account. Still the same error.