Do not clean off waxy stuff on your takedown joint. It turns out that it makes the sleeve fit tighter, it eliminates any tiny bit of play. If you remove the wax then the bow makes an awful flinch-inducing squirrel-scattering WHACK! every time its shot.
The noise sounds exactly like an out of tune arrow slapping the riser of the bow as it flies. It also occurs as the string is coming to a stop, which makes the noise happen just when an arrow slap would. If you are getting perfect bareshaft flight but your bow is noisy then this could be your issue.
To diagnose, de string and check for any wiggle in the sleeve. I had only a tiny wiggle, but it was still super noisy. The sleeve should feel rock solid, not even a hint of movement.
The fix is easy, its an old fishing trick to tighten up the joint on a 2 piece fishing rod. You take a candle (or some string wax) and smear it all over the male part of the joint. When you put the bow back together the joint should no longer have the wiggle.
I've never heard anyone talk about this before, and I just had a heck of a time fixing it. Trying to pass the word on so no one else goes on a 3 day tuning goose chase.