My NDS makes a clunking noise. Normal or not ?

I’ve just got my NDS back from Salisbury. I’d sent it back to them because I’d noticed it made a nasty rattling clunking noise whenever I lifted and moved it (gently of course). I assumed something must have gone amiss with the suspended brass plate inside, so off it went 5weeks ago. I got it back yesterday. Apparently, they could find no fault, but replaced the suspension springs for the brass plate as a precaution. They tell me they’ve tested the unit and all is well. However, the clunking noise is still exactly the same as before. Straw poll time: can anyone else tell me if their NDS feels or behaves like this when you move it ? Mine feels like there’s a heavy chunk of metal moving very slightly from side to side and there’s an associated slight rattle/clunk. A movement in the centre of gravity can also be felt in my hands. Can’t be right surely?