MS20 mini: case is live

[graspee]

I have a MS20 mini; I'm in the UK but I bought my synth from Germany so I have an official Korg power supply for Germany with an adaptor to plug it into UK socket which was supplied by the dealer.

When plugged in to the mains, even with nothing else plugged in to the synth (no headphones, mixer connection or patch leads) and even when the synth itself is turned off on the on/off + volume knob, the metal case is live. You can feel it if you run your finger over the metal case; if you touch the synth somewhere else to ground it then running your finger over the case is normal.

My questions, if anyone can be so kind as to answer please, are: Has anyone else noticed this same problem? Is the synth safe from damage? It seems to perform normally but is it? Would fixing this myself be easy? (I don't really want to open the case, but nor do I want to have to ship the synth back to Germany).

Thanks in advance.