MIDI input problems. Please help!

My first thought was that MS might be responding to the “key press” and “key let go”, believe this would generate two notes.
Another option is that the keyboard is echo back the information it receives from MS. If you do not use the midi output from MS, try turning that off in Preferences to see if that resolve the issue.
The keyboard also seems to have a possibility that is actually outputs MIDI different depending on the patch being used. It seems to have “layered patches” which could sent double notes.

Hope this helps in finding the cause.