What is making that ticking sound? NASA Greased Lightning

[RAM]

They are using brushless motors but it sounds like there are gears or some other mechanical noise.
Any ideas what would cause that sound?

 

[rcbif]

Can you point out when? I hear camera case or vibration close to the camera.

 

[RAM]

Can you point out when? I hear camera case or vibration close to the camera.

You can hear it in the first few seconds and again towards the end. I can't tell if it's there all the time because of prop and wind noise. I'm starting to think it's from the mechanism that rotates the wing and tail. It sounds a little like sonar.