HubConnection.Error handler is not called on connection error

[igolets]

I'm using package id="Microsoft.AspNet.SignalR.Client" version="2.4.3" targetFramework="net48". Using Azure SignalR service with backend deployed as Azure WebApp.

Steps to reproduce

1. App connects to server, reach "Connected" state
2. Client subscribed to Closed, StateChanged, Error events. Error event handler suppress all exceptions.
3. Shut down WebApp.
4. Run Connection.Start() from Closed event handler

Expected behavior

1. StateChanged (Connected -> Reconnecting)
2. Error ("Unable to connect to remote server")
3. Error ("Couldn't reconnect within the configured timeout of 00:00:05, disconnecting.")
4. StateChanged (Reconnecting -> Disconnected)
5. Closed()
6. Restart by calling connection.Start()
7. Repeat until connection is back.

Actual behavior

1. StateChanged (Connected -> Reconnecting)
2. Error ("Unable to connect to remote server")
3. Error ("Couldn't reconnect within the configured timeout of 00:00:05, disconnecting.")
4. StateChanged (Reconnecting -> Disconnected)
5. Closed()
6. Restart by calling connection.Start()
7. After repeating this several times I get unhandled exception.

Exception type:
Microsoft.AspNet.SignalR.Client.HttpClientException

Source:
Microsoft.AspNet.SignalR.Client

Exception message:
StatusCode: 403, ReasonPhrase: 'Site Disabled', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
{
Connection: close
Date: Tue, 26 Sep 2023 15:06:55 GMT
Content-Length: 2342
Content-Type: text/html
}

Stack trace:
at Microsoft.AspNet.SignalR.Client.Http.DefaultHttpClient.<>c__DisplayClass5_0.b__1(HttpResponseMessage responseMessage)
at Microsoft.AspNet.SignalR.TaskAsyncHelper.<>c__DisplayClass31_02.<Then>b__0(Task1 t)
at Microsoft.AspNet.SignalR.TaskAsyncHelper.TaskRunners2.<>c__DisplayClass3_0.<RunTask>b__0(Task1 t)