Was out yesterday with the grandkids and the wife found a deep snow drift and low and behold got stuck up on it (took tracks off -stupid move) - what I saw was that the right wheels where spinning but the left side where not - until she put the right brake on - then the left started to spin - when she let off the right brake - left side stopped spinning again - I was under the assumption that all wheels are to turn when brakes are off. ->> Question - is this normal for these machines or do I have a problem?