Istio Keeps On Showing TcpProxyValidationError Errors I initially created an EnvoyFilter to apply idle_timeout of 5s to outbound requests originating from workloads with label app: mecha-dev.
apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: tcp-idle-timeout
spec:
  workloadSelector:
    labels:
      app: mecha-dev
  filters:
    - listenerMatch:
        listenerType: SIDECAR_OUTBOUND
        listenerProtocol: TCP
      filterName: envoy.tcp_proxy
      filterType: NETWORK
      filterConfig:
        idle_timeout: 5s

However, the filter did not work for me and I found out it was because my cluster is using istio v1.2.5 which is a very old version and does not support EnvoyFilters properly and the envoy API for the same have been deprecated.
Therefore, I deleted the EnvoyFilter using kubectl.
But, even after deletion of the filter the istio-proxy sidecar containers keep on showing me the following error again and again:
[2021-05-11 11:59:14.109][22][warning][config] [external/envoy/source/common/config/grpc_mux_subscription_impl.cc:73] gRPC config for type.googleapis.com/envoy.api.v2.Listener rejected: Error adding/updating listener(s) 10.155.0.113_443: Proto constraint validation failed (TcpProxyValidationError.StatPrefix: [&quot;value length must be at least &quot; '\x01' &quot; bytes&quot;]): idle_timeout {
  seconds: 5
}

I deleted the pods and re-created new ones but this error keeps on showing up. Is there anything else I need to clean up or delete to get rid of this error?
Restarting Istio controlplane should fix the issue on hand (pods in istio-system, most likely pilot).
More importantly do not run Istio 1.2 its very outdated version with many bugs and security issues.