MF-108M | Why do the knobs behave differently after pluggin a cable into a CV input?

The MF-108 and MF-105 nominalize the CV to the mid point of 2.5V when not actively used. This allows an external CVs to pull the CV value in both the positive and negative direction from the knobs, unlike the other Moogerfoogers where the CV only adds to the knob position.  This arrangement increases flexibility in that CVs are bi-polar in nature. This means that when the knob is in the middle position a 0-5V CV gives full sweep range and conversely, when the CV is in the middle the knob has full sweep range.