Assuming you have a reasonably good grasp of the fundamentals, whenever you make a shooting error, it's because something in your shooting form has stopped working the way it should. When it becomes a repetitive error, or a series of different errors, it's because you have lost awareness (or maybe never had good awareness) with what your body is doing, and therefore can't self correct. Sure, a coach could look at you shoot and say "do this" and you could correct that particular error, but that's something your body should be doing for you on a non-verbal level every time you make a shooting error.
Awareness is the key to sustained good shooting. It is a two-pronged goal: getting it, and keeping it. Increasing awareness can be a life-long study that goes way beyond archery. However, a start toward increasing awareness is to realize that your body is constantly sending non-verbal signals to your brain about everything that is happening in your body. Mostly, we ignore these signals on a conscious level unless something really bad starts happening. But we can learn to feel these things on a more subtle level if we want to. For example, we normally ignore back tension, because in everyday life, it pretty much takes care of itself. But we can train ourselves to be aware of back tension if we want to, as we can with torquing the string, raising our heads, and a variety of other things that are helpful to archers.
Once we become aware of a particular subtle body function, we can correct errors before they become repetitive. However, it doesn't take much to block our awareness of these signals. It is impossible to feel these signals while having cognitive thoughts, i.e. thoughts expressed in words. Feelings of judgement or doubt also block awareness. So to be able to self-correct errors, we need to shoot without cognitive thoughts and feelings of judgement or doubt. I have never talked with a good shooter who hasn't mastered this.
So if you get in a slump in the middle of a tournament, ask yourself what's going on in your mind. If your mind is full of thoughts about how to correct the problem, or feelings of judgement or doubt, then you have identified what you need to correct to get out of the slump.