There are so many CASIO clones in China, some of them even clone the diagnostic screen (press shift, 7, on at the same time, then press shift several times, it will show the hardware version and ROM version). However the clone models don't have the same bug on CASIO models which can cause an upgrade. (I mean, software bugs)
Interstingly, the fx-MS series seems still be produced. I thought CASIO has stopped producing them. Can you check the producing date?