Highlighting objects problem (using TFormVector)

I have a strange problem with the setBox function below. Basically, when the player clicks on a unit in my game, the setBox function determines the 4 corners of the entity, and the drawRectCorners function draws lines at these 4 points to highlight the unit.

However, the highlighting seems to be much bigger than the entity. You can see what I mean below:


Now here is the strange thing - if I replace the 3d models with cubes (using createCube), it works pefectly which indicates that the code is correct and maybe it is the models that are the problem (but the models seem fine to me).

Any help would be most appreciated.

Function setBox(obj)
;calculate corners (screen coords) of entity

	map\boxW#  = MeshWidth(obj)
	map\boxH# = MeshHeight(obj)
	depth#  = MeshDepth(obj)

	width2# = map\boxW# / 2
	height2# = map\boxH# / 2
	depth2# = depth# / 2
	
	CenterX# = EntityX(obj)
	CenterY# = EntityY(obj)
	CenterZ# = EntityZ(obj)
	
	map\boxX# = scrnWidth
	map\boxY# = scrnHeight
	x2# = 0
	y2# = 0
	
	TFormVector -width2#, +height2#, +depth2#, obj, 0
	CameraProject cam\camera, CenterX#+TFormedX#(), CenterY#+TFormedY#(), CenterZ#+TFormedZ#()
	Points(0,0) = ProjectedX()
	Points(0,1) = ProjectedY()
	
	TFormVector +width2#, +height2#, +depth2#, obj, 0
	CameraProject cam\camera, CenterX#+TFormedX#(), CenterY#+TFormedY#(), CenterZ#+TFormedZ#()
	Points(1,0) = ProjectedX()
	Points(1,1) = ProjectedY()
	
	TFormVector -width2#, +height2#, -depth2#, obj, 0
	CameraProject cam\camera, CenterX#+TFormedX#(), CenterY#+TFormedY#(), CenterZ#+TFormedZ#()
	Points(2,0) = ProjectedX()
	Points(2,1) = ProjectedY()
	
	TFormVector +width2#, +height2#, -depth2#, obj, 0
	CameraProject cam\camera, CenterX#+TFormedX#(), CenterY#+TFormedY#(), CenterZ#+TFormedZ#()
	Points(3,0) = ProjectedX()
	Points(3,1) = ProjectedY()
	
	TFormVector -width2#, -height2#, +depth2#, obj, 0
	CameraProject cam\camera, CenterX#+TFormedX#(), CenterY#+TFormedY#(), CenterZ#+TFormedZ#()
	Points(4,0) = ProjectedX()
	Points(4,1) = ProjectedY()
	
	TFormVector +width2#, -height2#, +depth2#, obj, 0
	CameraProject cam\camera, CenterX#+TFormedX#(), CenterY#+TFormedY#(), CenterZ#+TFormedZ#()
	Points(5,0) = ProjectedX()
	Points(5,1) = ProjectedY()
	
	TFormVector -width2#, -height2#, -depth2#, obj, 0
	CameraProject cam\camera, CenterX#+TFormedX#(), CenterY#+TFormedY#(), CenterZ#+TFormedZ#()
	Points(6,0) = ProjectedX()
	Points(6,1) = ProjectedY()
	
	TFormVector +width2#, -height2#, -depth2#, obj, 0
	CameraProject cam\camera, CenterX#+TFormedX#(), CenterY#+TFormedY#(), CenterZ#+TFormedZ#()
	Points(7,0) = ProjectedX()
	Points(7,1) = ProjectedY()

	;set box coords & size
	For n = 0 To 7
		If Points(n,0) < map\boxX# Then map\boxX# = Points(n,0)
		If Points(n,1) < map\boxY# Then map\boxY# = Points(n,1)
		If Points(n,0) > x2# Then x2# = Points(n,0)
		If Points(n,1) > y2# Then y2# = Points(n,1)
	Next
	
	;calculate width & height of box
	map\boxW#  = x2# - map\boxX#
	map\boxH# = y2# - map\boxY#

	;add offset of camera view
	map\boxX# = map\boxX# + cam\viewX
	map\boxY# = map\boxY# + cam\viewY
End Function

Function drawRectCorners(x, y, w, h, size = 10, lw = 2)
;draws corners of a rectangle

	xw = x + w
	yh = y + h
	
	;top left corner
	Rect x, y, size, lw, True
	Rect x, y, lw, size, True

	;top right corner
	Rect xw - size + lw, y, size, lw, True
	Rect xw, y, lw, size, True

	;bot right corner
	Rect xw - size + lw, yh, size, lw, True
	Rect xw, yh - size + lw, lw, size, True

	;bot left corner
	Rect x, yh, size, lw, True
	Rect x, yh - size + lw, lw, size, True
End Function