Bad Smoke

Hi there, I'm looking for some advice on this bad smoke incident I had on my kettle. I put half a chimney of unlit briquettes on one side and about a half chimney of lit on top, and three chunks of hickory on that. Then I put ribs on and kept the temp around 275. I had white smoke for a bit and then no real visible smoke and it smelled great. About two hours in I had the lid off for a few minutes while I wrapped my ribs for the third hour. During that time I noticed that two of the chunks of wood were small, black, charred and looked pretty much spent, while the third chunk was barely burned at all, it just had a small amount of black on one side. This third chunk caught back on fire while I had the lid off. So I put the ribs back on and closed the lid. But the smoke coming from this third piece of hickory was almost grey and smelled bad. I gave it about 20 minutes but it wouldn't stop producing this bad smelling grey smoke. So I pulled that chunk out and finished the day with just charcoal. The bottom and top vents were about 1/4 to 1/2 open throughout the day. So I'm wondering if anyone knows why when that third chunk of wood caught that it didn't produce a white smoke and then change to no smoke with a nice smell like the other two chunks did?

Yeah that ashtray smell is what I'm talking about. So when a wood chunk is producing that grey ashtray smoke you just keep the lid off for awhile to let it burn off some more?