Not 2 months old yet with 1700 miles, got the triangle and "handbrake malfunction", "hill hold not available"and the car and wiggly road yellow symbol lit up.
Worries worries sorties. Needn't ! Stopped, turned off and then on again, all warnings symbols cleared. Result with fingers crossed.

I've also have had the "car and yellow wiggly line" symbol come on a few times on start-up indicating that autonomous emergency braking is not available. Every time I have restarted the engine and it doesn't reappear. No big deal (as it rectifies itself) but I'm going to mention it to the dealer if I happen to drop by or certainly when it goes in for its first service.

I don't know about the "handbrake malfunction", but the error about the brake assist being unavailable is common on really bad weather (heavy snow) or when the front sensors are covered in mud/snow. Once you clean the car, things should be back to normal.

I've had it happen to me twice already, both times in heavy snow, so no big deal.

Had this error with the handbrake,it also affected the cruise control not engaging. It was the clutch sensor which needed to be replaced as after it was reset it just kept returning the error every few miles.

It was a fine day then a torrential thunderstorm then fine. then the warning ...

Thanks Skbar247, hope it doesn't return considering newness of the vehicle