Great Stroller, bad tires

We've had our bugaboo frog for a year and have had to replace one tire and currently we can't use our stroller at all as all 3 of the rear tires we own are deflated and we are unable to find the leak. We use the stroller daily on walks around the city but don't use it for any heavy duty walking (sand or snow). The first time we had difficulty with the rear tires was a week after purchasing the stroller and the bugaboo company responded quickly and sent us a new rear tire. But our current struggle has not been addressed by the company and we are frustrated that a year after buying this expensive stroller it is virtually useless. Other than the tires we have loved the stroller and our daughter loves it too--it provides a smooth ride and we find it quick and easy to collapse. While we'd love to be able to recommend this stroller to others, the rear tire issues have really caused us a lot of frustration and ultimately we regret we purchased the stroller.