ASP.NET SignalR not disconnecting idle clients

Question

When my clients goes idle without terminating the connection, the ASP.NET SignalR server doesn't close the connection and disconnect the client.

I have a ClientTimeoutInterval of 10 seconds and a KeepAliveInterval of 3 seconds. My client can stay idle for hours and will not be disconnected.

What could be the cause of this? Surely there's a way to terminate idle clients...

builder.Services.AddSignalR(options =>
{
    options.ClientTimeoutInterval = TimeSpan.FromSeconds(10);
    options.KeepAliveInterval = TimeSpan.FromSeconds(3);
});