This test show that the issue is about the AMP ENV for some reason jump directly to the Release on the first step in a ARP/ SEQ.
Confirmed ... this totally drives me nuts and it took a while, until I found out, that
the click on the start of an ARP/SEQ (even certain factory presets) is a Bug.
The only workaround for this is to set the release of the Env VCA to a minimum of 0.08 ... at least to get rid of the click sound.
I hope this gets fixed in the next update, cause until then, the ARP/Seq is pretty much unusable in a DAW. At least this bug doesn't affect timing on a DAW track.