There is indeed something strange going on. I'm not getting a steady DC effect here, as knob position affecting pitch in a steady manner (is that what you get?). However I observe 2 things, using self oscillation of the filter to clearly hear the effects:
1 - When turning the knob out of the center detent it gives a little DC'ish spike before reaching the zone where the modulation takes effect. That spike can not be held it seems, it just goes "uuuubiiiuuuu", decreasing in pitch as I pass through that point, and when turning it back to land at the detent again, I get the same spike only increasing in pitch.
2 - VCF 1 is being modulated instead of VCO 1 when I (a) go to the left of the detent, then exactly to the detent, then to the left of the detent again. This can be 'cancelled' by (b) going once to the right of the detent, then to the left of the detent (now VCO 1 is being modulated as it should be). After that, action a can be repeated.
This bug is 100% reproducible here.
