Don't know what model of Transit you have - our Custom 270 which has a max nose weight of 112kg. Some of the models with heavier payloads are notorious for having a very stiff ride when lightly loaded & can skip sideways with lateral loads.
We used to tow a Lunar Clubman SE (1495kg) with our Transit Custom.If we didn't have at least 95kg nose weight we had the same problem. Once we got the nose weight right, it towed like a dream