See users group thread with msg 72878 and https://sourceforge.net/mailarchive/message.php?msg_id=27470464
The issue with the intellibox is that it has no flow control and that the internal buffer is quite small.
To get around this the intellibox will echo the command received over the built in interface back to the send, this then indicates to the sender that the intellibox is ready to receive more data.
Quite old ticket, but since there has been some significant changes on the Intellibox interface in the last few days, what I can say is that everything is working fine with the current development version (will be 3.11.1) with BOTH Intellibox-I (or Intellibox IR) AND Intellibox-II. So I propose to close this ticket.