A great example of 'inbreeding' not causing the same problems with reptiles as it does with mammals is the Sirtalis tetraenia population in Europe. It's a garter snake species native to a very small area around San Fransisco. Illegal to catch own or sell in the US now (I know a guy who got in mild trouble for getting too close to take a picture of one). About a hundred years ago, a population of 12 individuals was shipped to Europe, and it's a very popular species. Now, almost a hundred years later, the majority of those snakes are still healthy and look good. Odd traits are a bit more common (I've seen several 2-headed babies...) but overall the population is doing well.
In other words, after 100 generations of sibling or parent/offspring inbreeding, you still get healthy pretty reptiles.

Edit:
Some reptiles like the Brahminy blind snake are actually all genetically identical. There are no males, and the females self-fertilize, or mate with themselves. That species has been around for a very long time. lol, self-cest is even more inbred than incest.