'The fridge must be level in order to work' it says. How far off can it be? Our drive is a 10% slope so I've not bothered trying on it, but wondered what tolerance the 'fridge has to slopes. It's been so cold when we've been away that I'm not sure I'd have noticed if the fridge was working or not! Especially on gas - there seems to be nothing to indicate success other than the green light coming on when you switch it over. Do we just have to wait for it to warm up before realising we're parked on too steep a gradient?