The arp and expressions are not in time in Cubase 10.5 (latest) on Mac 10.12.6. when using the internal Scaler sounds or when routed to an external instrument . If however you drag the midi to CB it sounds fine. This is in both VST3 and 2. It seems to get progressively worse and is not as noticeable when plugin is initiated first. Tried turning asio guard off just in case that was the issue, no difference.
It sort of sounds like a buffering issue in the plugin trying the spit out the notes, the first note being ok and then erratic timing