Here's a quick check and should explain what is happening. Your chain is massaged data coming from a vendor - next time you see nothing in the chain try to pull up a quote which - most likely - is pure OPRA data. No quote going out to OPRA and all kinds of bells, whistles and lights go off. If you can retrieve a non-chain option quote the vendor that generates your chain or the in-house technology that generates the chain has a concern. I'll bet you can get a fresh quote even if the chain has dropped it especially in a name like AAPL.