Makes 2 cups instead of 1 when you only want 1

The machine makes 2 cups when you press just 1 cup. When you press a cup size (e.g. medium or big), as it starts grinding, it says "1 cup" as it should. However, a few seconds into the grinding, it automatically (by itself) turns to making "2 cups". This doesn't happen all the time, but enough to make it very annoying, not to mention wasteful. Thanks in advance for any help.