Display doesnt follow pressure

Normally the units work great but i started oout an dnoticed bike wouldn't turn well. Found the phone indicated 42 PSI where i set it on front and back. Removed the sensor and phone didn't change. I released the sensor and reinstalled. now it seems to be working. Bike had been stored for a couple months. but last time i checked the display was right. The graph showed no readings last 7 days. Any Idea what happened, Didn't check battery but unit is about 9 months old. other senso is fine.