My Mavic is that old, my gimbal was replaced 4-6 months ago by DJI.Interesting. That's likely an earlier build. I got mine just this week as a brand new unit from Best Buy, and it was manufactured September, 2017. So hm.
Not going to worry about it. Even if a motor is whirring like that for one second when it shouldn't, it would likely take a LOT of doing that to break anything.
Pure conjecture, of course.