All censors running wild today!

Today I discovered my altitude was over 4000m. Tried to calibrate and GPS says 615m. Pressing calibrate ok and it jumps back to over 4000 again, every time.
Temperature says 18'C, use to be around 30, (wrist temp) altitude now 8847m and barometric pressure 226..! Tried on/off but still crazy! What is happening?? Doomsday on its way?