I’ve made a sh*t ton of macaroni salad over the years and I have never had the problem you are explaining. If not sealed well the top layer might become dry, but never noodles sticking together. I cook my pasta, normally elbows, then once cooked I immediately chill in cold water, both to stop cooking and to cool because I will generally mix by spoon and or hand. I only use mayo, no oil or vinegar in macaroni salad along with the other ingredients.
(salt - pepper - parsley - celery chopped fine - carrots chopped fine - sweet gerkin pickles chopped fine - pickle juice added to taste - green olives chopped fine) I love using the sweet pickles and green olives for a sweet and salty balanced taste you don’t normally find in macaroni salads.
