Pro 2 - Omnisphere freaking out

[Exposure]

 Hey guys, hope you're good.

Absolutely loving my Pro 2 - it really is the best synth ever, so good!

I've set it up to control omnisphere as per this article - https://support.spectrasonics.net/manual/OmnisphereHW/2.5/en/topic/dave-smith-pro-2

However occasionally it freaks out and creates random noises - pitch / resonance / horrible artifacts. I also have to re-open the instance of Omnisphere to get the patch back.

any help much appreciated.
Thanks