Sure, if I remove ceiling drywall. The sag (gap) isn't across the entire 10' partition wall, and where it does sag, it's about .06 on average (the thickness of a tongue depressor).
Ok, so I removed 8" of drywall because the screws didn't eliminate all noise at wall. In doing so, I noticed that a non load bearing wall had a gap between the sub and baseplate. And a few of the stud had a gap at the top of baseplate. It's this relationship that's likely causing the noise...
Thanks, CJ. If I install .25" underlayment, undercutting the banister base wouldn't be possible. If I scrap the underlayment, it's doable. I'll look at various trims before making my choice -- carpet or LVP.
I used a tie plate over a T&G seam that's making terrible noise which completely eliminated the sound in THIS spot. If I stay with carpet, you can't really feel the bracket with the carpet down. And that's with a fiber pad which is only a quarter inch thick. If I swap out for new carpet with a...