Screws backing out may (repeat, MAY) indicate that there's already some damage to the brass from the heavy loads it's experienced. Fingers is right, however; the only real fix is to ensure the threads (male and female) are clean and free of grease or oil. Avoid the temptation to overtighten them; that will only make it worse. Just hand tighten to 'firm'.
By the way, plain water is all that's needed to clean real black powder fouling also. Really.