2014 tail gate jammed, now hit and miss

Hi all,
2014 T3
My tailgate wouldn't open last weekend. managed to get open eventually by locking/unlocking and banging the boot lid.
Now continually pressing boot release button It now open about 8 times then is hit and miss.
I have check the button by bypassing it with a piece of wire, same happens.
I have purchased a now boot release catch and same happens,
Only thing I can think of is the relay. I have removed the glovebox.
First I changed the fuses to check it wasn't them.
When pressing the release you can hear a relay clicking but it seems to be inside the fuse box.
it is one like this. Are the relays inside here? Assume you have to replace whole boards if it is.

Anyone shed any light on this, or advise what else i can check.
Or it is a thing that after so many releases its stops working?
One thing that did baffle me (as I haven't got a wiring diagram) is why is there three wires to switch and solenoid?
thanks
Darren