Using Openshift 4.10 and Helm 3.8, upgrading to persistent enable true, statefulset results to error

[paubengero]

Environment: Openshift 4.10
Helm: 3.8

Initial install was made using the in memory type buffer, it was working perfectly alright, no problems.
Now another helm install/upgrade was made after updating related values in values.yaml to enable persistence (use storageClass: "" for default provisioning as well) and shift to file buffering

helm upgrade -i --namespace=openshift-logging openshift-logforwarding-splunk charts/openshift-logforwarding-splunk/ --set forwarding.splunk.token=<HEC-TOKEN>

This results to error below:

Error: UPGRADE FAILED: cannot patch "openshift-logforwarding-splunk" with kind StatefulSet: StatefulSet.apps "openshift-logforwarding-splunk" is invalid: spec: Forbidden: updates to statefulset spec for fields other than 'replicas', 'template', 'updateStrategy', 'persistentVolumeClaimRetentionPolicy' and 'minReadySeconds' are forbidden