Maybe if you explain your setup a bit more (include a picture perhaps), and what you actually change when you connect your K2 in stead of the JU-06 we can understand a bit more what is going on.
Realise it was a bit unclear, but the K2 and BSP can only be connected by plain old MIDI Din.
So the BSP was set SQ1 (Midi 1) SQ2 (Midi 2) Drum (Midi 10) All fairly normal. But with all patterns cleared, on all projects and all sequences I was still getting a rhythmic scale of notes.
The JU-06 could be on any channel but would still receive these random notes.
I hooked up the JU-06 to the output of MIDI-OX via my normal Akai audio interface and it showed no issues.
I hooked up the BSP to the input of MIDI-OX via my normal Akia audio interface and it showed no notes being played on any channel… but “RT” was being triggered “System Realtime??”
I presumed this was some sort of clock although not too familiar with MIDI.
I tried to disable the clock output in Artuira Midi Control Centre but this did not seem to work.
I then found the option to change the clock source on the JU