Found this forum as also experiencing problems with Pioneer AVIC-F77DAB (Euro equivalent of 8100 NEX I believe) along with Siri, Carplay and Bluetooth on an iphone 6s running 9.1. Looks like this will be a good resource for sharing information and hopefully finding a solution to the issues I'm experiencing.
Previously was using a 5s that worked fairly well with Carplay on the Pio. I'm not sure which update broke it or if I have a hardware issue with the Pioneer. I suspect a combination of both at present. I say this because apart from Carplay not working as well as it did I have lost navigation voice guidance for the both the Pioneer nav and the Maps nav when connected by cable (Carplay). I also cannot hear callers when using the hft either by Carplay or when connected via bluetooth.
I can get voice guidance with Apple maps over bluetooth and this is about the best I manage. I find it ridiculous that all this expensive hardware doesn't work like it's supposed to and the problems just change from update to update. Hoping the next ios update fixes things but I'll believe when I see it! Also going to contact Pioneer UK this week to see if they can shed any light on the issues I'm having