I have used the xfce4-terminal, as well as the xfce panel with the openbox window manager on a Ubuntu 14.04 kernel (3.13.53 linux kernel version), and had a similar problem.
I used the default option on the xfce panel initially which displayed the top panel and the second xfce panel as a dock on the bottom. As a work around I deleted the second panel (the dock), and re-added the second panel at the bottom and elongated its dimensions to have identical dimensions as the the top panel.
The xfce panel has settings which you can adjust by right clicking the panel, selecting panel, and selecting panel-preferences. With in panel-preferences you can delete and add panels as well as change each panels settings. This may be the option you are looking for. Another alternative which I employed, which is a work around all by itself and is to install and configure cairo-dock.
Using cairo-dock you can configure it to show each individual occurrence by selecting the integrated option under the behavior setting.
By doing so the dock will show each individual initialized terminal resting on the dock as shown below.
Best of luck and go UBUNTU!
Sorry Rivi, I just read re-post, you might ordersorting: