Hello,
I received my unit, turned it on and used it for a short while. Then, switched off, i turned it around to check it out from all sides and and at some point i heard something "rolling" inside - like a loose part. I also felt something was moving there but much heavier - which was the battery.
As some other customer posted before me, the small loose part was some electronic component (a crystal?) which was bumped a lot by the battery during transport and at my home finally knocked off by merely turning the unit around - no sudden moves by me.
I suggest to better secure the battery and avoid it reaching into that crystal.
In my case the pcb was damaged at the place where the crystal was soldered and had to "bridge" the connection with a thin copper wire.
Regards
Florin
Thanks for the feedback.