2008 Nissan Navara tow bar too low

I had a tow bar fitted at a reputable garage as soon as i got the vehicle. The first time i towed with it the cable on my trailer was damaged. I thought the tow bar looked a bit low but there is only one place it can bolt on so therefore must be right. However, i took it back to the place that fitted it and they couldn't fathom what was wrong and why upon measuring the tow bar it seemed to be a couple of inches lower than any other navara they'd seen. They had a look underneath and suggested the leaf springs didn't look right, and that i should take it to nissan and get it checked over. I did this and after checking the ride height etc and leaf springs they said nothing was wrong with it and cannot think why the thing just looks too low. So basically, I now have a brand new vehicle for work, that if i put anything on the back of ends up getting damaged!!