If the grill is operating strangely, it is important to do a visual inspection of the fire grates to ensure they are sitting correctly in position. The image below shows this exact situation, where the fire grate is out of position.
The fire grate can be kicked out of the correct position if the ash dump handle is used too roughly and let go like a pin-ball machine, causing the left fire grate to jump up out of position.
If the above occurs, remove the fire grates, clean out all the wood pellets and ash – replace correctly into position and fire up as normal.