OK, a baffle is a metal plate that is place at the top of the opening of the firebox where smoke and heat enter the cooker. The baffle keeps flame from entering the cooking and chamber will help keep ash out to a degree.
If the vents to the firebox are facing into the wind, gusts can move enough air through the cooker to deposit ash in the cooking chamber. Placing a wind break infront of the firebox can help.
Look into installing a baffle and consider the weather conditions when your cooking.