vertex points disappear in mapping editor

hi! I'm messing around with the mapping editor in V9 and I lose the vertex points in the right window from time to time.



as you can see in the screenshot I have the object selected and "edit mesh" activated, however the output window always shows me the soft-edge borders and my vertex points are black, so it's really hard to see them with a background-image like this. all the other projectors work fine, is there any hint to get my nice bright vertex-points back?

and the auto map function works pretty decent from time to time, however other times I lose my projector somewhere up in space, the number fields for position and rotation show only #NAN and the output is black - any ideas on that?

I might have a cure for this, but I'm having a hard time getting the verticies to disappear ( ive seen it happen, but I don't know how to induce it ) - any "tips" for getting them to disappear?