hi,
a similar problem here, win 7, studio one 4 (keylab 61 mk2 firmware 1.0.10.23). to be precise, as soon as the necessary mackie control device is added and connected with the midiin2/midiout2 ports, as soon as i play a note without any aftertouch, keylab 61 mk2 sends aftertouch (aftertouch 1-5) messages on the assigned mackie control ports for a while - then it stops.
ps: being forced to fill out a captcha and the two additional questions is a nogo - it just annoys as hell. and i'm i a lot of forums.