
No idea but I can tell you Remy does a similar thing - his back hocks kick out sideways as he walks, just a little. Nothing wrong with him to cause it though - I assume it's just bad breeding (he is pet bred and atrociously so, inbred, and his conformation is all wrong for a dobe).
Might be worth checking hips and knees (thinking luxating patella - maybe the pup is trying to compensate for pain)? I've heard of an entire litter of cocker pups having practically no hip joints through malnutrition of the bitch, they couldn't use their back legs at all to begin with.