So I've been brewing British ales off and on for the past year. Throughout, I've had some issues with off-flavors. I can't for the life of me sort out what it is, nor can I put my finger on what the flavor is. It's not specifically 'off', it's just a slightly ?flat? flavor in the fermenting wort and in the finished beer. I've posted elsewhere when this happened before and people suggested fermentation temps being too high, but the past 2 times have been between 16-20C, so that's ruled out. The only other constant has been S-04 yeast, but I'm not clear on what specifically is wrong or not here. I've got an English IPA in the primary now, and it has the same off-flavor. If I let it sit in the glass for a while, some of that seems to gas off, making me wonder whether it's perhaps relate to the yeast? Is there any way I can off-gas the whole batch or does anyone have any idea what might be leading to this and how I might prevent it in the future? FWIW, this beer is Maris Otter/Caraamber/Wheat/Biscuit with Challenger/EKG, mashed at 65.5C for 75 mins.