First post... I just signed up now due to this weird issue.
Can you think of any scenario where the multidrive knob would send filter control messages?
I loaded up a MIDI monitor and I can see that multidrive knob sending both controllers 18 and 19. (19 being the filter, if I'm not mistaken)
If I move the filter knob a bit, this stops happening and the multidrive knob behaves normally.
A bit more testing and it seems like I need to have the filter knob around 12 oclock for this to happen. It won't happen if the filter knob is anywhere else.
So bizarre... I hope this is user error. I've got it plugged in via USB. Running the latest version of Ableton. I have the vst plugin for the sub37, but it's not running at the moment.
(edit) Most experimenting.. I can get the filter knob to sit just over 12oclock and all of a sudden it starts spitting out control messages. And as I sweep the knob, I can hear the filter jump open a bunch.
D