When you attach a small object to the fuselage of an aircraft and put a camera near to it, if you watch it carefully by camera during flight, you can see it will vibrate in cycles (becoming more and more violent, and stop, and become violent again and again…). If an object's surface is very close to another's surface, it will "flash" during such vibration (as you can see in the GIF above). Also, no matter whether you are in atmosphere or in space, as long as you are moving, this bug occurs, and it seems every part will vibrate.
This bug has been existing since the first time I played SR2(0.8.107). It really annoys me since I am making a detailed dashboard of an aircraft and this shake sometimes makes instruments unreadable and terrible to look at (like in the GIF above). I hope someone can look into it and fix it !
@AndrewGarrison Now at least it makes sense to me, thanks for your explanation!