Ticking noise when turned on?

[agour]

I just noticed my new unit makes a sort of fast ticking noise from the rear of the unit when powered on, before powering the motors on.

I don't remember my first unit making this noise - is it normal?

It's not the fan, as that comes on later and is a lot louder.

 

[thetech]

The ultrasonic sensors on the bottom make a ticking noise.

 

[Robbie]

I am also having this same issue. I noticed when i took off today that the drone was starting to wonder on its own and i then brought it down to land and it didn't stop itself before landing. I then had a look at it to find that there is a ticking noise coming from the ultrasonic sensors on the bottom. Im just wondering what might have caused this to happen as it seems to have knocked out the downwards sensor system