So far there are only certain combos that cause death - referred to as lethal combos - not single genes. The closest thing to a fatal single gene is desert females who can die of complications if bred, thats why female deserts are sold as pet only. Spider wobbles almost never interfere with the animals ability to function (even if they act funky). Youre more likely to hatch out a hatchling kinked from an incubation issue than have a spider that fails to thrive due to spinning.
It depends what the problem is. Sometimes people dont mind (spiders wobbling) and others it crashes the price of the morph (infertile desert females). Inbreeding does happen occasionally, but 1-2 generations is usually perfectly fine. Remember, inbreeding does NOT cause issues, it only exposes pre existing issues that had been hiding.
Usually if anything is deleted or ignored its because there are still a lot of people out there spreading bad information. Its still common for people new to the hobby to talk about breeding the infertility issues out of deserts by adding more genes. Comments along those lines are frowned upon because it will likely just lead to a lot of dead animals.