DIAGNOSIS The grease management system is overwhelmed or misaligned. The drip tray channel isn't directing grease to the bucket effectively.
FIX Check the slope. The grill must be perfectly level front-to-back so grease flows to the rear drain. Use a small level on the grill grates. Adjust the legs. Then, ensure the V-shaped drip tray is centered so its channel aligns directly over the drain hole.
IF THAT DIDN'T WORK You're likely cooking excessively fatty meats without a drip pan. For long cooks like pork butt or brisket, use a disposable aluminum pan on the lower rack or directly on the drip tray to catch the bulk of the render.
HEADS UP Never let pooled grease accumulate. It's a major flare-up risk. Clean it after every long cook or high-fat cook. The 'super smoke' mode at low temps exacerbates grease pooling as it doesn't burn off.