...and if that doesn't give good results, the burner gas outlet holes may be dirty as well. If you have a small drill bit set, you can use a size just smaller than the holes to run in and out by hand...this should knock any burnt-on drippings and/or dirt out. To remove it completely, you should blow out the holes with compressed air while the burner inlet is faced downward.
Sometimes the best way to keep them working properly is to perform these maintenance tasks about once per year. It will help to avoid getting into a jamb when planning a smoke and finding things aren't working correctly, and also to keep you up to speed with what it takes to keep things working right. My 1.25 year old Smoke Vault 24 is acting up in a similar fashion too, so, I best get with the program myself...LOL!!!!!!
Eric