My M3P now gives this message along with its panic alarm almost every time I drive it. It rarely actually applies any steering input and on no occasion is any correction required! It even went off in Tesco's carpark at <10mph last night! I wouldn't mind if you could switch the damn thing off permanently, but you can't, it keeps resetting itself each time the car is used.
Reading the forums suggests that this is a known problem and is caused by poor software. I have seen it suggested that if enough people keep booking services for this issue, Tesla will become sufficiently annoyed to actually do something about it. I have booked a service appointment to see what happens.