100-year-old stairs pulling away from wall. And there is a little give.
Call the installer, builder or manufacturer for any warranty type of repair...I'm kidding. Your best bet is to get a Carpenter or Stair Builder that uses glues, screws & bolts behind or even upon the finished surfaces...finish screws are wonderful.
Nails, spikes & staples are the norm & they can't & won't last, they're held by friction alone. Glue Coated nails are only good for a decade at the most, glue only lasts if its hold can't flex or break loose. A stair is a moving part, if given the chance, & will only continue to loosen until another object retains it.