Gas oven. the burner in the oven keeps getting clogged and it sets off the carbon monoxide alarm,

Question

the burner in the oven keeps getting clogged and it sets off the carbon monoxide alarm, also does not keep up baking temperature, we notice a problem when the air vent at the top starts putting out small particles and it takes longer to cook.

I take it all apart and it is full of soot, it should not happen every month.
Please help