u/Massive-Emphasis8411

I buy Costco brand k-cups. In a box of 120, most of them will taste fine, but about 10% of them will make a very bitter and unpleasant tasting cup of coffee. The pods that taste off always have a concave top like on the left, and the normal tasting ones are convex like on the right.

At first I thought the manufacturer was being sneaky and throwing in cheaper, lower quality Robusta beans instead of Arabica, but now I think it has to do with how the k-cup is being sealed given the shape difference.