Wow, this sounds like a total clown-car operation:

Out of the first group of 30 dogs, only four managed to detonate their bombs near the German tanks, inflicting an unknown amount of damage. Six exploded upon returning to the Soviet trenches, killing and injuring soldiers.

and later...

Another serious training mistake was revealed later; the Soviets used their own diesel-engine tanks to train the dogs rather than German tanks which had gasoline engines. As the dogs relied on their acute sense of smell, the dogs sought out familiar Soviet tanks instead of strange-smelling German tanks.