Here is a helpful solution for the common causes:

• Improperly blended dry ingredients
  SOLUTION

  Since biscuits, scones and shortcakes should not be overmixed, it’s very important to mix dry ingredients together well before cutting in the fat. If they are not well mixed, there can be pockets or lumps of ingredients; this is particularly true with leavening, which can lead to bitter or off flavors. Learn more about leaveners.