/emulators/virtualbox-ose Serial port access?

[Anthony Takata]

So I have battled my way through various forum posts and sites around the
internet, and I think I have whittled my issue down to something weird in
VirtualBox.
Basically, I am trying to pass a serial port into a VM for the purposes of
running a fax modem.
The modem appears on the FreeBSD host as /dev/cuau0, and I can use Minicom
to open it and perform various AT commands at the host level.
So, I have set a Windows 2012 VM to put the port as Com1 using the Serial
Device /dev/cuau0.
The problem is, communication is highly erratic inside the Guest, most
characters not coming or going correctly, even under a simple HyperTerminal
session. It is almost like the CTS pin is permanently active but the actual
device is not really ready for data.

Is this a known issue?
Using VirtualBox 4.3.18_OSE on FreeBSD 9.2

Apparently the users and Oracle are pointing the finger at the
oh-so-highly-customized-we-dont-know-what-they-did-to-it FreeBSD version of
virtualbox, and will no lift a finger to help diagnose the issue.