Last Tweaked Option not working

Hi all,
I'm using FL Studio 12.1 on Windows 10 with an M-Audio Axiom MIDI controller, and I've had this problem for a long time. I cannot seem to link any controller knobs to individual parameters other than the Modulation and Pitch Bend controls. For instance, I use Arturia's Minimoog plug-in, which allows me to link a parameter like defCutOff to the Mod Wheel. Then if I try link say defEmphasis to another knob, it doesn't work, and just seems to hold the link previously made. So, I have twelve obsolete knobs on the controller.

I'm not hugely savvy when it comes to MIDI, but I have played about with the various options, volatile links etc and have had no luck. I bet its a simple fix too. Here's hoping someone has answer!

Thanks
Joe