Maybe someone is just messing with your head, ya know waiting for you to leave your phone and changing stuff on it.
Back in college we found a friends keys to his car and would go into and just move stuff around did it for awhile then started putting new CDs in his player then one day put a Hawaiian Bobble doll on his dash and just enjoyed watching him kinda lose his mind till we got him drunk and tol dhim... Ohh the simple pleasures
sorry that was no help , I'm not sure why it's doing that. I've had mine give the completely wrong temp the other day it was almost 70 degrees and it was telling me that it was -3degrees .. And all the cities were right