Dangerous Adaptive cruise control

[Joningy]

My 3 week old MGS5 has developed a significant and potentially dangerous problem with the ACC, it doesn't always turn off when pressing the the centre of the 3 left side steering wheel buttons, (the button showing a steering wheel pic)

To set ACC, I'm pressing the left centre steering wheel button, followed by pressing the left steering wheel toggle button to set the speed.

To turn off I press the central of the 3 buttons, or brake pedal.

BUT pressing the centre button on the left side steering wheel doesn't always disengage the cruise control, it keeps going at the set speed, although the screen shows it turned off, ie the light changes from green to white (I think it's green to white!)
If approaching a junction at perhaps 40 to 60 mph it can be very scary, especially if there is a car in front of me as it keeps trucking on at the previously set speed.

It does eventually turn off, but taking several seconds and not instantly as it should do and sometimes does, it only seems to be a problem over around 30 to 35 mph, below this speed it works as intended (so far)

I contacted the main dealer's service department, I received an unsatisfactory response from them like "we haven't seen many of them yet" NO offer to look into it.
To reiterate, it stops instantly by pressing the brake pedal!

Has anyone else experienced it?
Can anyone explain if I'm not carrying out the correct procedure (can't see this, but it's a new car, my MG4 never gave me a problem)

 

[5teep]

I normally just tap the footbrake but if your buttons are not working as they should get it in to the dealer.

 

[Joningy]

I normally just tap the footbrake but if your buttons are not working as they should get it in to the dealer.

Hi there @5teep , yes I'll pop in on Monday, we are at the dentist 200 yards away from the Main Penton dealership in Salisbury, it was lunchtime when I rang on Friday, a girl answered the phone and went off to ask someone, they sell Citroen (spit) as well so my guess is, they cover for each other I'll see the main guy at the service desk tomorrow. cheers!

 

[Alb]

I've seen this happen so you are not alone!
Not really a concern to me because if there was any degree of urgency behind disengaging ACC I'd be using the brake pedal regardless.
Just another example of flaky software I expect.

 

[Anon70]

Do you see the same behaviour in speed limit mode as well as ACC mode? This will help to indicate if it is a button issue or a software issue.

 

[Alb]

I don't think it's a button issue because selection works 100% of the time. It's only deselection that has an intermittent glitch.

 

[Joningy]

Do you see the same behaviour in speed limit mode as well as ACC mode? This will help to indicate if it is a button issue or a software issue.

Almost certainly a software issue @Anon70 , the button actually deactivates the ACC, well it turns the light from green to white on the driver display, but it takes perhaps 5 or more seconds to switch off, that's way too long for many people to actually deactivate, as I've mentioned braking works as it should, maybe it'll give the dealer a few scratching heads, I'll keep the thread updated as I'm sure it could cause a nasty situation in the wrong hands!
Maybe just a fatory reset will fix it, but MG should know about it.