Sign up for a race or event that you have never done before. This will force you to change your training routine and add new methods and exercises to your regiment in order to get prepared for it (at least this is what I like to do).
Have you considered that more recovery may be needed? Is the pre/post workout nutrition being optimized? Is the “wall” power, strength, or endurance, etc. related? If I don’t have the necessary information, I can’t begin to give an answer.