Diagnosis
Grease fires happen when fat drips onto the heat diffuser plate, gets super hot, and ignites. The DLX's design can be prone to this if you don't manage the grease runoff.
How to Fix It
The key is the drip tray and the disposable foil liners. Before every long or greasy cook, make sure the sloped drip tray is correctly installed under the grates and is covered with a fresh, heavy-duty foil liner. That liner should be changed frequently. For big briskets or pork butts, consider adding a second disposable drip pan on top of the grates to catch most of the drips directly.
If That Didn't Work
Your temperature might be too high for what you're cooking. A lot of grease splatter happens at 350°F+. For fatty meats, try running at a lower smoke setting (like 225°F) for longer to render the fat more gently.
Heads Up
If a fire starts, do NOT open the lid. Turn the dial to 'Shutdown' and let it run its cycle. Opening the lid gives the fire a huge burst of oxygen and turns a flare-up into a cannon.