OK, a bit of background first.
My 3DR Y6 had been sitting in the attic for a couple of years, so I dusted it off and got it back in the air. I still need to tune it, but I flew it first in front of my house (just hovering), and then decided to take it to a field near by and do an auto mission. I should point out that I reset everything, but the drone is flying OK (as I said, I still need to run Auto Tune).
Anyway, last flight lasted a bit under 10 minutes, and I am checking everything now. When I looked at the vibrations, I am OK in X and Y, but rather high on Z.
My question is how do I get rid of vibrations on the Z axis? I would imagine X and Y are the props, but what causes Z vibrations?