I was doing 6 racks of bb"s for a 1st b'day party for my granddaughter when I thought that after an hour or so my egg was burning hot and the ribs were a little too far along. I pulled my Tru Temp and tested it in boiling water and found that it was registering about 70 degrees too low. I re-calibrated it and continued the cook at about 210-225 dome. I had about 37 people that would have been hugely disappointed If I hadn't caught it. I did 2 racks on my Small, which had the original temp gauge from BBG, which I also tested and was dead on. and they all came out great.
From now on I'll test my gauges before each cook. This is my 2nd Tru Temp. You can't be too careful.