Technically that could be overcome if you don't care about individual specimen welfare and mutate until you get viable specimens. It won't be quite the same but it would restore a viable species.
Mutations are very rarely viable. In fact, the original cloned animal mutations must be eliminated in order to have viable future generation. The only thing that (may) benefit from mutations is the imune system. See the problem with cheetah's lack of genetic variability: https://en.wikipedia.org/wiki/Cheetah#Genetics
Mutations are very rarely viable. In fact, the original cloned animal mutations must be eliminated in order to have viable future generation. The only thing that (may) benefit from mutations is the imune system. See the problem with cheetah's lack of genetic variability: https://en.wikipedia.org/wiki/Cheetah#Genetics