Shifting bridge and nut
Instruments- discuss specific features, luthiers, instrument problems & questions
Both the bridge and nut look to be in slots. If I am understanding correctly, the issue is that they do not fit snugly into the slots and are not glued into place, so the bridge and nut are being pulled sideways in their slots by the force of the low D string.
After seeing the photos, I definitely think that you should remove the strings, and then glue the nut and bridge into place, taking serious care to make sure that they are perfectly centered on the fingerboard, and also being very careful to make sure that the nut is held firmly in place while the glue sets. you seriously want to avoid leaving any kind of gap between the nut and the fingerboard, as that will mess up your intonation. On some dulcimers, the bridge and nut can be replaced for different string arrangements, but your bridge and nut have slots for both of the common arrangements, so probably the bridge and nut were not intended to be sitting loosely.
