FWIW, dmtaylor helped me with a tip to try a few years ago:
the boiling point of acetylaldehyde is around room temp (high 60s, low 70s). if the beer is kegged, you could bring the keg up to room temp and degas the keg. if not carbed yet, bubble up some CO2 through the beer out post to help facilitate getting the acetylaldehyde out.
thankfully, I don't (KOW) run into this nuisance anymore, but I do know I tried this twice over the years and it did definitely eliminate it once, and lessened it another time if my memory serves me.