MIDI keyboard is resetting my compressor threshold?

How and why is this happening? I have an AKAI MPK88 plugged in, but I'm playing an audio track. I mess with the compressor on the audio track, and, apparently randomly, the threshold gets reset to 1. Sometimes when I'm toggling the compressor on and off to compare sound, and sometimes just when I'm playing through the audio track.

I'm not aware of any active signalling from my keyboard - no buttons are pressed, no pedals...

When I unplug my keyboard, the problem (so far) disappears...