Most likely, you do have a hole blocked in the grate, or at least some partially blocked. I had to clean the holes in my grate once already this year, and I see that I'll have to do it again. Let the hopper empty out completely, and remove the grate when it's cooled off. Then clean the underside with a wire brush and the holes with a drill using a 1/8" bit. I usually then clean out the area under the grate with the Shop-Vac as ell as the whole inside as long as the fire is out. Hope this helps you out.