Weird sound when selecting a patch/rig containing the "chromatic pitch" effect

Hi

When selecting a patch/rig containing "chromatic pitch" from a Midi foot controller or the "cross"-buttons on the Kemper, I'm getting a weird noise present on the first notes before the proper pitched sound kicks in. It's worse on distorted sounds and comming from another bank.
Even if I wait a few seconds after selecting the patch, it kind of waits for my first note to twist it.

But .....
This weird sound doesn't occur if I turn on and of the effect by pressing the fx-button on the front of the Kemper. The "chromatic pitch" effect works instantly with no artifacts in sound.

I'm in Performance mode, but I don't think it matters.

Anybody else having this issue?

cheers
F

Nope, no expression pedals.
Only a Boss FC50 (sends PC) to switch rig/patch on the Kemper. The noise is pulsating a few times and then stops. I can switch into the rig, wait, and it is quiet, but as soon as I hit a note the noise appears, pulsates a few times and then the sound is ok. The Midi command is then sent ages ago.

thanks anyway

F