No, I don't think it has its own battery - maybe for the clock but it does not really need that as it has GPS sync. At least it has not got the totally illogical, alien power control system that Mazda have fitted on my wife's CX-30 - every time you even go NEAR the car in possession of the key fob it powers up a multitude of systems and if you happen to leave a door open, whilst vacuuming for example, then it powers up even more circuits "ready to go" with the result that if you take too long or do it too often without driving the thing in between times the result is a flat or even deep discharged battery!
Probably just a glitch in communication with some module or other as you say.
I have done 2 updates on my Kona N and both have involved different procedures - the first, after it had done about 20 mins of "Verifying" told me to switch the engine off and the update would then continue, the second most recent one insisted I leave the engine on all the time?
It also usefully informed that leaving the engine idling (for up to an hour) may breach local regulations - really helpful! I have always (on this and previous vehicles with similar systems) gone for a drive whilst it is updating - that's the beauty of having an automatic transmission, as long as you remember to disable the start/stop thingy then you know you are not going to stall or stop the engine.
Disappointing, seeing as the vehicle has its own built in data SIM, that it won't do OTA updates itself overnight or something.