This page details one limitation, which the team is aware of: mute not working or working inconsistently with other articulations.
As might be expected, inserting a nat. as well as mute off removes mute… in one case at least - that of the (Bass) Trombone.
This is analogous behaviour to restoring an arco after a pizz. in strings before Dorico 1.2.
Has to be said: thanks Daniel and team for adding NotePerformer 3 - and to Arne for his excellent support !