I own the subject calendar.
Something odd happened yesterday. AAPL was up a few points, but the Oct 640 Call dropped in value approx 10%. HOWEVER the Sept 640 call gained a few % in value. The IB IV indicated that IV dropped on both calls but actually the IV drop in Sept was greater. I can't go back and look at historic IV now or the historic price.
I just found this odd, and I was wondering if it was signaling something I didn't know about like some major positive announcement in Sept and negative announcement in Oct? Is this type of behavior common?