Step 1: Find someone who has not lost “it” to check over your recurve and your arrows to make sure they are okay. Just okay, no need to be perfect. This will give you confidence that your recurve and arrows are capable of performing as they should.
Step 2: When someone's groups go from baseball size to 12.5” at 15 yards, it's very often because they were concentrating on the spot when they shot the baseball sized groups, and lost their focus when they shot the 12.5” groups. You state that you are able to achieve baseball sized groups, rarely, which means that it wasn't just a fluke. You KNOW how to achieve baseball sized groups.
Work on your concentration. You KNOW you should be concentrating on the spot from the time you start to aim until the arrow is in the target. You THINK you are concentrating on the spot from the time you start to aim until your arrow is in the target. You're just not DOING it.
From the time you start to aim until your arrow is in the target, no words should pass through your mind. If any words pass through your mind, let down and start over. Do open your mind to all sensations from your body. If you feel something from your string hand, open your mind to the feeling, so you can think about it (in words) after the shot is over. This is the way we learn to correct errors, because even though we have learned how to do something in a class, we're not always going to do it correctly, but our body will tell us, if we listen to it. We are capable of feeling physical sensations at the same time we are concentrating on the spot. We are not capable of thinking in words while we are concentrating on the spot.