Hello,
Welcome to out family of the best forum on the internet.
Stay calm and don't panic, because it will not bring any solution

Important to know is :
a. On what midi-channels do the six (?) play ?
b. Did you 'multi-layer' your MS50's keyboard ?
c. Check MIDI-settings as TxD (send channel) for left, right, chord..... etc. perhaps you have 'doubles'.
d. Some soundcards have initial THRU settings.
At first you could give me (us) the MIDI-settings that are shown on your display after pressing the MIDI-button.
I don't know Jazz++ but I expect the software is able to give you details about every recorded note ?!
It is important on what ch. the notes are recorded.....NOT the TRACKnumber but the MIDI-channel.
Roel