The bug is quite straightforward - when I change the pitch or bearing (i.e dragging/rotating) of the map, the Cube seems to shift position despite being set to fixed coordinates.
I've put together a Sandbox to demo this bug. Change the pitch or bearing (i.e drag/rotate) the map and you will see the white Cube move relative to the red square (which is fixed). Expected behaviour is that the cube should be fixed relative to the red square.