Stupid question here but have you tried new batteries? The supplied batteries did not last very long in mine and I started getting readings like that.
Weber WSM, Weber GA, Weber Spirit S-320
Charbroil Oilless Turkey Fryer
Wife LuzziAnn 1956 model.
Maverick ET-732, Superfast LSU Purple Thermapen
The Fun Never Stops at the BBQ Brethren Throwdowns
2013 Throwdown Grand Master. 1/2 of Team Paradise.