In the video below, I have a contrabass tuba playing an E eighth note.
In the Spitfire Symphonic Brass library, articulated contrabass tuba notes are assigned to keys an octave higher than the unarticulated notes (don’t ask me why), so to get a marcato note to play at the correct pitch, I have to set Transpose to 12 for that technique in the expression map.
When I apply a marcato articulation to the note, it plays at the proper pitch. When I then disable the Marcato technique in the expression map, the note plays an octave higher than it should. (To fend off the obvious question: Yes, I have double-checked that I am not transposing the Natural technique.)
I can confirm that this is a bug: Dorico is incorrectly applying the Transpose value from the switch when the switch is disabled. Thanks for reporting it: I will make sure it gets fixed at the earliest available opportunity.