Double clicking a marcato accent misplaces it, when changed from default.
Confirmed by Marc Sabatella, and he asked that I post it here.
I went into Style/General/Articulations and Ornaments and changed the positioning of marcato accents (and others) to above the staff (the system default being below). Works properly if I drag the accent to a note, worked properly to reposition all the accents when I hit "Apply" after making that change, or if I go back in and hit "Apply", also repositions them if I copy a section with accents below to another site (or even to the same site), but if I select a note or notes and double click the marcato, the accents go below.
Happy to submit a measure or two to show this if necessary, but I think the explanation should be enough.