Maybe I'm missing something, but isn't possible that the the "normal" female is a really normal looking new variant of the BEL complex? In which case we'd also say that the clutch hit bad odds in that 50% weren't BELs.

I understand the other explanation that the null phenomenon may have occurred in this baby, but then one would have to assume that the mutation occurred very early in development for the snake to be completely affected, and not look like a paradox. It will be interesting to breed it out, but one has to keep in mind that the mutation may not necessarily be expressed in all the cells of the snake, such as in the reproductive cells. Very cool stuff.