Calico's - Any lethal combos to stay away from?

[C&H Exotic Morphs]

i can agree to disagree. as i said earlier, i didnt mean lethal as in you would have to deal with dead or deformed babies, but i consider a "lethal" combo any combination of genes or alleles that is incapable of producing living offspring, in which case spider x spider, calico x calico, and (maybe?) pin x pin is.

And this is the issue.
All 3 of those pairings produce living offspring.
You don't end up with a greater number of eggs going bad during incubation, hatchlings dying in the egg, or deformed babies.
So how exactly are they incapable of producing living offspring?

Eggs can't be reabsorbed or become slugs after a female Ovys. And the males sperm doesn't met the follicle until a female Ovys. So if these pairings were "lethal" you would have some visual issue with either the eggs or hatchlings right?