Really interesting what you are writing, though - honestly - I have no clue what might be the cause for that. I got the free Violin from Virharmonic and sure, it is pretty reduced and not comparable to the Bohemian, but that also does work fine for me. I loaded a Schubert string quartet and replaced Violin 1 and 2 by Virharmonic and the playback runs as expected and without dropouts.
Would be interesting to see how UVI/Bohemian behaves in Cubase, because Cubase and Dorico share basically the same audio engine. You could get a free trial of Cubase Elements from here: Try Cubase now for 30 days | Steinberg