I noticed an unfortunate behaviour in my module, which is that when a marker is placed on a unit counter, it is not placed “on top of this piece” as it is specified in the trait, but always goes “on top of stack”.
Incidently, it also does not match the rotation of the unit counter, even though the marker also has “Can Rotate”, and Place Marker has “Match Rotation” set.
I use Vassal 3.6.19. I doubt that this is a bug in Vassal, because it would have been discovered long ago, so what could I have done wrong?