SOAP UI 5.3.0 - HTTPS - java.lang.IllegalStateException: WRITER

I configured a simple Mock Service both in http and https (keystore, etc)

In http it works, in https I got the following error:

2017-03-22 12:26:06,456 ERROR [errorlog] java.lang.IllegalStateException: WRITER
java.lang.IllegalStateException: WRITER
	at org.mortbay.jetty.Response.getOutputStream(Response.java:594)
	at com.eviware.soapui.monitor.JettyMockEngine$MockRequestLog.log(JettyMockEngine.java:691)
	at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:51)
	at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.Server.handle(Server.java:326)
	at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
	at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
	at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
	at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
	at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
	at org.mortbay.jetty.bio.SocketConnector$Connection.run(SocketConnector.java:228)
	at org.mortbay.jetty.security.SslSocketConnector$SslConnection.run(SslSocketConnector.java:713)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

When i call the HTTP URL i see on the HTTP response (RESULT=OK)

When i call the HTTPS URL i see on the browser this:

There are currently 1 running SoapUI MockService

HTTP MOCK

Is it a bug ?

The same behaviour with SOAP UI 5.0.0

Thanks

Andrea