Question: After manually binding the device with its drivers it is working fine, but when you connect the device to another port the device appears as unknown in the Device Manager. Why is this happening? What is the solution?
When you connect the device for the first time, you have to bind it manually with its drivers. Once this is successful, the device will work fine and you can plug and play in this port. If the drivers are not digitally signed, and if you connect the device to some other port (unused port or connected through HUB), the device will appear as an unknown device. You have to bind it again to make it work properly. This has to be done for every unused port.
This problem does not appear if the serial number in the device descriptors is a non-zero value. To avoid this problem, use a non-zero serial number in the device descriptors.
For more details refer to Enabling driver use with all USB ports.