Spider can be so variable, it could just be the right subtle genes combining in a certain way, but I bet if it's something you really like, you could work on some line breeding and make something a lot more obvious and predictable in your line.
I'd avoid Stinger x Spider as well, but I'd probably just breed the Spider to her own male non-Spider OS at some stage with higher likelihood of picking up those patterns. Maybe there is a particular morph male that combined with her might draw it out even more or help understand what is going on better.