Audio clicks at stacks when changing parts

There is an audio click on stacks when changing parts, even if both parts are the same and no inserts, (one is a copy of the other)

Is the audio input signal continuously applied, or is it silenced between transitions? Put differently, does it produce click in both cases? Also pls let us know which plugins are inserted, thanks.

Hello. No plugins. Same audio input from a RME Babyface on a MacBook Pro with Catalina.

So, while changing, is there continuous input signal?

Yes. Example a guitar, that needs to increase fader value for a solo. Maybe needs a sort of crossfade between parts or thomething…