Sear plates installed incorrectly- Ensure sear plates are installed with the holes towards the front, and the slots on the bottom. The group of five holes must be in the center of the grill. See assembly instructions. Improper pre-heating Pre-heat grill with both main burners on high for 10 to 15 minutes.
Excessive grease and ash build up on sear plates and in drip pan - Clean sear plates and drip pan regularly. Do not line pan with aluminum foil. Refer to cleaning instructions