kubernetes e2e tests fails with spec.configSource: Invalid value

We are running kubernetes(1.15.3) e2e tests via sonobuoy and 3 of them fail with the same error:

/go/src/k8s-tests/test/e2e/framework/framework.go:674
error setting labels on node
Expected error:
    <*errors.StatusError | 0xc001e6def0>: {
        ErrStatus: {
            TypeMeta: {Kind: "", APIVersion: ""},
            ListMeta: {SelfLink: "", ResourceVersion: "", Continue: ""},
            Status: "Failure",
            Message: "Node \"nightly-e2e-rhel76-1vm\" is invalid: spec.configSource: Invalid value: core.NodeConfigSource{ConfigMap:(*core.ConfigMapNodeConfigSource)(nil)}: exactly one reference subfield must be non-nil",
            Reason: "Invalid",
            Details: {
                Name: "nightly-e2e-rhel76-1vm",
                Group: "",
                Kind: "Node",
                UID: "",
                Causes: [
                    {
                        Type: "FieldValueInvalid",
                        Message: "Invalid value: core.NodeConfigSource{ConfigMap:(*core.ConfigMapNodeConfigSource)(nil)}: exactly one reference subfield must be non-nil",
                        Field: "spec.configSource",
                    },
                ],
                RetryAfterSeconds: 0,
            },
            Code: 422,
        },
    }
    Node "nightly-e2e-rhel76-1vm" is invalid: spec.configSource: Invalid value: core.NodeConfigSource{ConfigMap:(*core.ConfigMapNodeConfigSource)(nil)}: exactly one reference subfield must be non-nil
not to have occurred
/go/src/k8s-tests/test/e2e/apps/daemon_set.go:170

kubectl get nodes -o yaml gives these fields and yes, we do have kubelet dynamic config enabled:

spec:
  configSource:
    configMap:
      kubeletConfigKey: kubelet
      name: kubelet-config-1.15.3-1581671888
      namespace: kube-system

What are we missing?

Thanks.