Virtual Box 5.1.6 Problem

My host OS is FreeBSD 11 and VirtualBox version is 5.1.6. I built guest OS windows 2003 under Virtualbox 5.1.6. When I start guest OS, I cannot use USB device under guest OS. Can anybody know this and solve this problem?
Thanks a lot.
My OS is FreeBSD 11.0-RELEASE, my Virtualbox is 5.1.6, my guest OS is windows 2003. I upgrade FreeBSD 11 from FreeBSD 10.1. I use USB device under guest OS before I upgrade the FreeBSD 11.0 and upgrade Virtualbox from 4.x to 5.1.6.
my env is:
in my loader.conf:
in my devfs.rules:
add     path    'usb/*'         mode    0660    group   operator
and add user into operator group.
But when I attach usb device, there is problem, Can anybody fix this:
Failed to attach the USB device vendor 0x1483 product 0xc007 to the virtual machine win2k3_32_0.

USB device 'vendor 0x1483 product 0xc007' with UUID {b9788e2b-9e42-494f-8453-9a0d60fba728} is busy with a previous request. Please try again later.

Result Code: NS_ERROR_INVALID_ARG (0x80070057)
Component: HostUSBDeviceWrap
Interface: IHostUSBDevice {c19073dd-cc7b-431b-98b2-951fda8eab89}
Callee: IConsole {872da645-4a9b-1727-bee2-5585105b9eed}
There is some weirdness with 5.1.6 and 5.1.8 (USB host to guest pass-through not working) but you can use 5.0.26 and it just works fine like 4x.

Here is the port files download and replace corresponding directories under /usr/ports/emulators with the ones you extract from this compressed archive here >>

You`ll have USB support.
There is some weirdness with 5.1.6 and 5.1.8 (USB host to guest pass-through not working) but you can use 5.0.26 and it just works fine like 4x.

I've also upgraded system and the package at once and I was not sure if I should downgrade the system or the port only until I read this topic, the above info in particular.

Making the long story short: I've used ports-mgmt/portdowngrade to get the old version of VirtulaBox, but I had to delete the .svn directory from the downgraded port directory to compile it successfully.

I can confirm: FreeBSD 10.3 + VirtualBox 5.1.6 and the USB pass-through does not work. Works fine with VirtualBox 5.0.26.

And I have a question. Now the handbook says: Without the extension pack, the FreeBSD host cannot pass USB ports through to guest operating systems. The workaround described there in the past was removed from the Handbook. Is there any chance for the extension pack for FreeBSD? Is it a real technical problem and the sources of VirtualBox can't be patched? Or is it a political problem, I mean Oracle requested to lock this feature for FreeBSD?
(...) our port is an unofficial hack of the Linux version to get it working on FreeBSD.(...)

I hope that usb pass-through will return in some next version. But if it is more problematic maybe it is possible to add another ports to the tree with "old", I mean 5.0.x, version of VirtualBox?

BTW: I think that it is probably not good place to write it: Could the package virtualbox-ose-lite be compiled with vboxwebsrv option? VBoxManage is enough for headless emulation, but the service is more comfortable with phpvirtualbox, which requires vboxwebsrv.