CORS issue for server-side streaming

I am able to implement unary calls using grpc-web but server side streaming doesn't work as expected. When first open the page, CreateStream is called and works as expected. the network tab looks like this: (there's preflight response but not shown in the screenshot)

This is CreateStream 200 detail:

After around 1 minutes 30-40 seconds, there will be this error:

There will be another pending CreateStream when that error occured:

My envoy.yaml looks like this:

```
static_resources:
listeners:
- name: listener_0
address:
socket_address: { address: 0.0.0.0, port_value: 30800 }
filter_chains:
- filters:
- name: envoy.http_connection_manager
typed_config:
"@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
codec_type: auto
stat_prefix: ingress_http
stream_idle_timeout: 0s
route_config:
name: local_route
virtual_hosts:
- name: local_service
domains: ["*"]
routes:
- match: { prefix: "/auth." }
route:
cluster: auth_service
max_grpc_timeout: 0s
- match: { prefix: "/name_of_service." }
route:
cluster: stream_service
timeout: 0s
max_grpc_timeout: 0s
cors:
allow_origin_string_match:
- prefix: "*"
allow_methods: GET, PUT, DELETE, POST, OPTIONS
allow_headers: access-control-allow-origin,keep-alive,user-agent,cache-control,content-type,content-transfer-encoding,custom-header-1,x-accept-content-transfer-encoding,x-accept-response-streaming,x-user-agent,x-grpc-web,access-token,token, authorize-token,x-site-type,x-origin,x-pin-token,grpc-timeout
expose_headers: custom-header-1,grpc-status,grpc-message
http_filters:
- name: envoy.filters.http.grpc_web
- name: envoy.filters.http.cors
- name: envoy.filters.http.router
```
This error always occur every 1 minute 30/40 seconds. That means the red error messages in the console will be a lot if I don't close the page. I have also tried setting deadline on customer side but its no use. How to fix this CORS error? I haven't look at the cloudflare because idk what to look at, and also if cloudflare is the problem why do unary calls and the first server streaming call works? Thanks