If there's a heavy towball weight, you can certainly get the warning. To prevent it occurring, when towing my caravan I up the pressure in the rear tyres from 38 to 42. Reset the monitor once the caravan is connected.

If you reset the monitor when your trailer is connected (without changing pressures) you shouldn't get the alert. It is not kind on your rear tyres however, as the additional weight increases the sidewall flex and therefore the heat within the carcass. That can lead to premature tyre failure.

Good tip Anthony.