Where is all this supposed inbreeding of spiders taking place? Being a dominant morph, no inbreeding was ever needed to create bunches and bunches of them. SOME inbreeding might have been done to try and create the "super spider" but certainly not anywhere near the amount we've seen with recessive morphs that show no such genetic defect.
And if it was possible to "breed out" the wobble, then I would have thought it'd be a lot more rare than it is today.
I do believe it is some sort of neurological tweak that goes hand in hand with whatever gene gives us the spider appearance...and the severity of that "tweak" differs greatly just like the amount of white on their sides differs.