This issue only happens when connect with "wss://serverendpoint". Please refer to the attached sample test.
Both reproduced on Windows and Linux with latest 9 dev nightly builds.

It can be simply reproduced with following snippet :
//Server endpoint is a simple Echo server which just send the received messages back to the client.

WebSocket ws = WebSocket.newBuilder(
                URI_TO_ECHO_ENDPOINT, A_HTTPClient_WITH_SSLContext, A_Listener())
                .buildAsync().get();
        ws.sendText("Fist message");
        ws.sendText("Second message");

        // Then wait for all the replied messages

I double checked the server endpoint. The messages were indeed received and replied