The story of Kennel Club dogs is pretty much the same from one breed to the next:
A relatively small numbers of dogs are brought into the Kennel Club;
The registry is closed so no new genetic material can find its way in;
The show ring selection system results in a relatively small number of dominant (ribbon-winning) sires being elevated in the gene pool;
The breed splits due to differences between types (coat color, size, lay of the ear), further reducing the already-small gene pool;
An extremely condensed gene pool (10,000 dogs may have the genetic diversity of 50) means that negative recessive genes are able to easily find each other and double down within a litter, resulting in offspring with disease or deformity.
With any Kennel Club breed, the only three variables in this story are:
The genetic quality of the dogs in the original Kennel Club pool;
The length of time the dogs are in the Kennel Club, and;
The degree to which the breed standard calls for negative morphological selection.
The genetic quality of the original Kennel Club pool is obviously important, but it cannot provide salvation, for even a pool of dogs without negative genetic traits is doomed under a closed registry and show-ring selection system.