Anything related to missing notes has first to do with technique/fundamentals. If your hand is in proper position and you let your fingers fall (without reaching for notes), then you are on a good path. The second part which takes the most effort is repetition with scales. If you practice various scales for at least 10 minutes each time you practice, you will begin to see improvement in your concerto. It’s important to vary the scales that you do, as it’s all important training for muscle memory. Being that the violin is a fret-less instrument, it takes precision and accuracy that can really only be mastered by repetitive repetition.