Aún no hay datas especificas si es lo que quieres saber. Puedes seguir las betas que están abiertas actualmente en este post del blog oficial: https://blog.bq.com/es/programa-betatester/
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RE: Bluetooth Aquaris X (connection problem in car)
If you search the web you will find many other brands and devices with problems connecting to the old medianav (and to other hands-free systems). This happens because there is so many different multimedia systems, devices, and software versions in the market, that sometimes it's hard to guarantee full compatibility for every single combination.
Did you make any firmware update to your BQ or to the medianav system when the problem appeared?
If no, then try to reset your medianav and smartphone Bluetooth settings to factory defaults and see if that solves the problem.