The repair center has returned the camera.
All they did was "upgrade the Firmware".
Well, I had done that myself already. The Camera's firmware is still at the (latest) version that I had flashed already.
Based on the repair report, I'm worried they haven't done any physical inspection of the zoom lens mechanism and the procedure might have been unhelpful.
My suspicion is, they tried the camera very shortly and the problem didn't appear while they tested, as I had presumed.
At least the repair center was quick in processing the camera...
I'm back at "let's hope it was a one time glitch and won't occur again". I will report again if it does happen again, but let's be optimistic.