The shifting is probably as a result of the note being in voice 2.
If you want a notehead that stays attached to the right-hand side of the stem, try this:
In Write mode, select the uppermost note in the chord (C), press shift-I and enter 2 in the popover to add an interval of a second, then move it down a step using alt-down arrow. That creates a unison with a notehead on each side of the stem.