I don't think either of those theories are plausible. First, sperm just aren't that 'smart', and the ovum is encapsulated with none of the DNA available for the sperm to peruse. Second, one gene will not entirely delete a gene from the other chromosome.

From what I've seen, most of you introduce the male to the female well before she ovulates which means she is storing sperm. This can act to partially negate the idea that slugs are follicles that are bad from the go. Or if not a cause of the slugs, what might be happening is that the spider-spider combo is simply so lethal that the female resorbs it entirely due to failure to develop at all.