They frequently must be reset. Use a hinge pin as a nail punch. If you replace your deck or build a new one, we suggest that you use construction screws instead of nails. They take longer, but hold better. To find out if you have rot, poke a small penknife into the surface of the wood.
Soft spots are easy to detect and can be a warning that harmful fungi exist.
Rotted boards should be replaced. A fungicide can be applied to the new material to increase its longevity. Follow directions for use and wear a breathing mask. At hand and stair rails, gaps at joints should be caulked, primed and painted to prevent moisture attack. Remember, irrigation and sprinkler water can be just as damaging to wood as is rain.