It's being discussed here -
http://videokarma.org/showthread.php?t=274711
In a nutshell the infotainment system supports HD Radio. A proprietary modern "high-bitrate" radio format that's not going to end up like DAB in Europe, we swear. There is a data stream formatting standard that has to be followed but for some reason NPR didn't completely follow it or they managed to unknowingly find a bug in the implementation that meant the broadcast went out but it was malformed. Be it a textfile or an image, the file lacked an attribute that told the receiver what it was.
Mazda's infotainment build quality has been mostly questionable at best and nobody in Japan asked what would happen if an HD Radio stream was received that wasn't formatted to spec, or at least to ship it in the 2016 model they didn't test this. The result of the Seattle NPR gaffe was the receivers received the stream, had no idea how to handle the weirdness and crashed into a bootloop which bricks the system.
I still have no goddamn idea how in this day and age we can manage to screw up something as simple as a radio. It's about as bad as modern cars getting regular "bugfixes". Who the hell do you hire for programming and code auditing/testing?