I'm having a weird problem when modifying the bmap of a sprite in my game. I wanted to make a ring sprite that appears around a ship when it is selected. I created a function that edits the bmap of the ring so that it is the same color as the team's color (ie, orange team, green team, etc). This works great, unless i view the sprite from a far distance or at an angle that is not perpendicular to its surface. At times like this, the new bmap begins to fade out and the sprite's old bmap fades back in.

To show this better, my sprite is black with a blue X on it. When a ship is selected, the bmap is completelly written over by black with an orange ring:
http://img68.exs.cx/my.php?loc=img68&image=shotring3nr.png
This works great. However, if the sprite is far away and at an angle, the ring disapears and the X comes back:
http://img162.exs.cx/my.php?loc=img162&image=shotx4px.png

What is going on here?

3DGS version 6.3 Pro