@ravez said:
I had this issue before and it was just because of the remote keyswitch note that was actually in the playing in range of the contrabass, might be worth checking that out.
It might also be that you have inadvertently linked e.g the Celli articulation map instead of the CB one to the CB track.
The way you describe the issue seems to be linked to or in the CB track but you could mute all tracks then unmute one after the other to find the culprit.