Did the maverick fall off and is now closer to the fire? It has happened to me.
The difference you're seeing isn't big enough to make me think that it is broken. Usually, if it is broken it will be HHH or LLL or something. Check the wires. Make sure they aren't pinched or crimped. Make sure you're measuring at the same spot as the Weber. Make sure fat isn't dripping on the thermo.
Proudly Smoking on a UDS, PBC &
Accidental Winner of the 2012 "Saucy" Throwdown.