If you have one, does the Smart Key work?
Since the problem is intermittent, the dealer may not be able to reproduce the problem. But you should take it in and have them check it out. It could need a software update. Or maybe a fuse is not making good contact. Or maybe the brake lamp switch isn't working right. Maybe a loose ground somewhere.
And if they find nothing, take it back again the next time it happens.
It is a bit of a safety issue since you could get stranded in a strange locale, or need to move your car in the middle of the night to give access to emergency vehicles.
And it wouldn't be a bad idea to get and keep detailed receipts of your complaint and work orders in case it doesn't happen for a few years and you have trouble getting it fixed under warranty.