IIRC these types of solar events can cause some turmoil and even change the size/shape of the atmosphere. That can change how long it takes the GPS signals to g

IIRC these types of solar events can cause some turmoil and even change the size/shape of the atmosphere. That can change how long it takes the GPS signals to get to your phone, which can add noise to the trilateration calculations. Fancier receivers have some clever ways to mitigate that, but your average cell phone GPS chip may lose some accuracy.