This problem has just appeared in a new project. When I went back and tried all old project they all had a similar problem.
If I select an instrument in HALion the sound is perfect when I preview it. Having selected it, when I go back to the write or play window and play there is a horrible sound played along with the first note of playback. It varies slightly depending on the instrument selected, but it sounds like a bass note or some sort of drum crash and is 1 octave below the first note. Wherever I start playing from it always happens on the 1st note then gradually dies away.
I have checked all the suggestion on the Dorico audio troubleshooting video, but nothing changes.