Could be that some systems brakes even if the system is not on.
My wife´s VW Golf does that if you push it hard in to corners and there is a guard rail, **** dangerous if you ask me...
ACC on the 718 Cayman gives you two features both of which depend on the radar sensor located beneath the front number plate. The first feature is obviously the ACC itself, which allows the car to follow a car in front and brake down to a standstill (if necessary) and start off again. This is basically about stage 0.5 on the 5 stage car autonomy list - and this is about as far as Porsche have got so far. A standard Mini offers more.
Porsche ACC does not operate unless specifically selected - or, in my case, even when specifically selected. In other words it's OFF most of the time unless you manage to turn it on. No one in their right mind would turn it on when using the car on a track.
The other feature it offers is PAS (as I've said). This is ON all the time - according to Porsche anyway. I haven't yet been able to verify that, but I'll check it out because some of what Porsche say is not true in my experience. What this does is use the permanently active radar sensor to detect when the car is in danger of hitting the car in front and give an audible warning and prepares the brakes. If you persist in what the Porsche software thinks is dangerous driving it will give a jolt on the brakes. But it doesn't stop you - it just tries to make you aware of a possible problem. This seems reasonable to me.
Whether this actually works properly or not I have yet to find out. I can see the problems with the car taking control over from the driver because I was once given a Mercedes courtesy car which had a feature which tried to decide if you needed to an emergency stop by measuring how quickly you moved your foot from the accelerator to the brake. If you did it very quickly it immediately applied emergency brakes - which it did when I braked for roundabout. Seriously dangerous - they don't offer this feature any more. The Porsche's approach seems fairly cautious by comparison. My concern is that the PAS will kick in when I approach a corner - with a hedge behind it like a lot of country roads in the UK - at speed.
When I work out how to use it and the snow clears I'll report back.