i brewed an sam smith oatmeal stout clone from ahs 3 months ago. it was an extract batch with steeping grains. it has a very strange aftertaste. the initial taste is good, but the back end is terrible and i can't determine the off flavor. my fermentation temps have always been good and i've used all the equipment since then with no other off flavors. there is no sign of infection in any of the bottles. i am completely stumped. i have since moved to all grain, but i am still curious as to what went wrong in the batch. any ideas?