T5600 front USB3 motherboard header?

I have recently purchased a used Precision T5600.  The front USB3 socket was damaged when I received the unit (the blue plastic part that the pins are on was broken) so a USB plug could not be inserted.  Windows 10 also complained about a power surge on the USB port.  I disconnected the USB3 cable from the motherboard header and the error didn't return so I am guessing there was a short in the USB3 socket.

I ordered a replacement front I/O panel that came with the USB3 cable which I have now installed (an absolute pain to replace as it needs the motherboard to come out to route the USB3 motherboard cable behind it...).  Anyway it didn't work - either from within Windows or on boot.  Windows also now shows the Power surge error message when a USB3 device (portable hard drive) is connected.  The new USB3 motherboard cable has the 20-pin plug for the motherboard header and an angled USB socket that fits into the front I/O panel, however it is black plastic inside as opposed to blue like a normal USB3 socket.  I have checked out other Precision workstations with the same chassis and they all appear to have 1 x USB3 and 3 x USB2 sockets so I am guessing they are all the same?  Plus its a 20-pin USB3 header on the motherboard so even if the cable was wired as a USB2 socket (i.e. just using the USB 2.0 data pins on the USB3 header rather than the SuperSpeed RX & TX pins) then the socket would work as a USB2 socket?

I am tempted to buy a standard USB3 motherboard 20-pin plug to USB3 socket to test it as the Dell cables are a bit rare and rather expensive just to test with.  Is the USB3 motherboard header standard on the T5600?  Any other ideas on what could be wrong?

The rear USB3 port works fine and at USB3 speeds.

Cheers

Andy