Help! D50 transmitting strange midi messages to Y S90ES

[V-man]

Hi, newbie here!

I have an issue that I don’t understand. I want to play sounds from my Yamaha S90ES on the D50 keyboard. On the S90ES you can globaly set and store something called "Basic Receive Channel" which I have set to MIDI channel 8. This allow me to play the S90ES sounds from a external keyboard if the Transmit Channel on the external keyboard is set to the same Channel as the Basic Receive Channel on the S90ES.

I have a D50 where I have set the TX midi channel on some of the patches to channel 8 so I can play the S90ES sounds from the D50 when I choose certain patches. But as soon as I press the Bank/patch select buttons on the D50 to select one of these patches with the TX channel set to channel 8, the Basic Receive Channel on the S90ES changes to channel 1 with the obvious consequense that I can't play the S90ES sounds. Strange!!?? So my conclusion is that some kind of unknown MIDI signal or message is transmitted from the D50 that changes this Basic Receive Channel on the S90ES.

There is no setting in the S90ES where I can disable incoming MIDI messages on "global level" so to speak, so that gives no solution. In the D50's MIDI settings, both globaly and on patch level I have disabled all types of outgoing MIDI messages like Program Change, Control Change, SysEx and so forth. I only use the Patch TX channel setting to control the S90ES. I also have a Integra 7 which I control from the D50 without any issues at all.

I have learned via motifator.com forum that there is a SysEx message
that can change the Basic Receive Channel on the S90ES. This is how
this is done:

F0 43 10 7F 01 00 00 0A dd F7
where dd = Basic Receive Channel
00~0F hex is channels 1~16
10 hex is omni (all channels)
7F is off

I then made some MIDI input-output monitoring via MIDI-OX and that generated this data (sorry for the poor formatting):

Just to remind, the S90ES Basic Receive Channel is set to 8 but is mysteriously set to channel 1 when doing below actions.

MIDI-OX Input when selecting patch 58 that have MIDI TX ch set to 8:

TIMESTAMP IN PORT STATUS DATA1 DATA2 CHAN NOTE EVENT
000153E2 1 — BE 7C 00 15 --- CC: Omni Off
000153EA 1 — BE 7F 00 15 --- CC: Poly On
0001567B 1 — B7 7C 00 8 --- CC: Omni Off
0001567E 1 — B7 7F 00 8 --- CC: Poly On

MIDI-OX Output when selecting patch 58 that have MIDI TX ch set to 8:

TIMESTAMP IN PORT STATUS DATA1 DATA2 CHAN NOTE EVENT
0003431E 1 1 BF 7C 00 16 --- CC: Omni Off
0003431E 1 2 BF 7C 00 16 --- CC: Omni Off
00034326 1 1 BF 7F 00 16 --- CC: Poly On
00034326 1 2 BF 7F 00 16 --- CC: Poly On
00034BF7 1 1 B7 7C 00 8 --- CC: Omni Off
00034BF7 1 2 B7 7C 00 8 --- CC: Omni Off
00034BFA 1 1 B7 7F 00 8 --- CC: Poly On
00034BFA 1 2 B7 7F 00 8 --- CC: Poly On

Just as an example, below is what is generated when selecting
another patch of the D50 that have another TX channel set, in this
case channel 2.

MIDI-OX Input when selecting patch 83 that has MIDI TX set to ch 2:

TIMESTAMP IN PORT STATUS DATA1 DATA2 CHAN NOTE EVENT
000513E9 1 — B2 7C 00 3 --- CC: Omni Off
000513EA 1 — B2 7F 00 3 --- CC: Poly On
000517A4 1 — B1 7C 00 2 --- CC: Omni Off
000517A5 1 — B1 7F 00 2 --- CC: Poly On

MIDI-OX Output when selecting patch 83 that has MIDI TX set to ch 2:

TIMESTAMP IN PORT STATUS DATA1 DATA2 CHAN NOTE EVENT
000513E9 1 1 B2 7C 00 3 --- CC: Omni Off
000513E9 1 2 B2 7C 00 3 --- CC: Omni Off
000513EA 1 1 B2 7F 00 3 --- CC: Poly On
000513EA 1 2 B2 7F 00 3 --- CC: Poly On
000517A4 1 1 B1 7C 00 2 --- CC: Omni Off
000517A4 1 2 B1 7C 00 2 --- CC: Omni Off
000517A5 1 1 B1 7F 00 2 --- CC: Poly On
000517A5 1 2 B1 7F 00 2 --- CC: Poly On