X50 still sending MIDI data in Combi mode

[ogox50]

Why is my Korg X50 still sending MIDI data? Even if the combi timbre parameter MIDI status is set to "off" or "int" on all eight timbres and all the channels are set to Gch (global channel) . It is still sounding the tone generator of the synthesizer it is connected to.

The x50 is connected to the amplifier (to sound the x50 internal tone generator) and also connected to the another synthesizer via MIDI cable, X50-MIDI Out, external synthesizer-MIDI IN.

In Combi mode, I can make the external synthesizer tone generator sound and not the x50 tone generator.

But, in Combi mode too, I can make the x50 tone generator sound, but it is still making the external synthesizer's tone generator sound even if the MIDI Status in the Timbre Parameter is set to "int".

I want to play EITHER the x50 sound or the external synthesizer sound but not both. While they are connected as mentioned above.