These should be useful to several on here, so thank you for posting them.Mine had factory fit of the European removable towing Ball. It is identical to Westfalia one, we had two trailhawks alongside each other at the weekend and one was aftermarket fit and they are identical, apart from the cap that goes over the ball doesnt have "westfalia" written on it.
So, according to this thread, its either some of the smaller Nuts or the large Bolts that are missing.
I took a look under mine and took some photos, so this may help anyone that had one fitted in UK perhaps.
Bolts mentioned are ringed in black, nuts mentioned are ringed in red
Looking under my Jeep, its pretty easy to check if they are in place and thankfully they all are.
Nearside, on a UK right hand drive car:
Offside on a RHD car (drivers side):
Its an easy check to make, they can all be seen up underneath the bumper, if it is indeed these nuts and bolts.
In the UK, nearside is the left side and offside is the right side as though you are sitting in the vehicle facing forwards. So the location of the nuts and bolts should, I assume, be applicable to both left and right hand drive European and American models.