Error: UPGRADE FAILED: cannot patch "classic-rest-service" with kind StatefulSet

Some clients have run into the following issue:

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

The way to get around this is to delete the classic-rest statefulset and to rerun your helm commands/upgrade script.