pitch drifting down when controlling mini reissue by cv

[Sihaz]

Hi, have asked tech support about this but thought I'd check in with you guys too... I have been experimenting recently with driving my minimoog from my akai ewi - something I've been doing very successfully via midi with my sub 37. to get the same level of control on the mini though i need to go via a midi to cv converter - I'm using a kenton pro solo mkii. This set up works fine when driving an arturia minibrute but when I use it with the mini, the pitch drifts down imperceptibly but about a semitone every 30 to 40 seconds. I'm wondering if there's some calibration I can do on the mini to stop this happening or if any of you guys have any other ideas. Thanks in advance.