Theres a few ribbons in there, one transmits the information about the location of the af ring to the mainboard as in where between minimum focus and infinity the focus is, the other is the iris/aperture control ring, the third tells the lens what zoom the lens is at between 17 and 85 mm.
80% of the time one of the ribbons (usually the af) due to constant movement wears out and cracks, rest of the time its something physical, cogs, aperture blades, grit, damage due to knocks etc etc
ps sorry to hijack thread