Check your prop balance and make sure the motor mount is not cracked, check the motor screws are tight. Power train vibration is usually because the rotating part isn’t spinning true, props wear out, screws get loose, mounting holes open out. Stresses of use.
Can't watch the video right now because I'm in the middle of a long rambling work telecon, but in my experience I wouldn't expect any prop to come out of the box balanced. However, my own ASW28 from HK came out of the factory pretty ok. The other thing this could be is a slightly bent prop shaft (which can be hard to see.) Edit: also double check the motor mount screws haven't started to vibrate loose?
The motor without a spinner and prop has no load on it, so it will sound fine.
What about the motor mount and the shaft? What are the motor bearings like? Have you split the rotor from the stator to check the insides and the shaft?