3d widget suddenly gets transparent where there's a window behind, why?

I’m having a hard time figuring out why my 3d widget acts like this. Take a look: Dropbox - File Deleted
It’s supposed to be totally opaque, and I do not want the windows to shine through. And why that sudden change in behaviour when going closer/further away?
I did disable depth test on the engine widget material to make the widget still show when it clips a wall or floor. Any ideas what I can do to fix this? Thanks!

Just guess but did you try to tweak translucent priority? Set the widget priority to 1 and windows to 0

No, didn’t know such thing existed. I was aware of the z depth priority. I’ll try it first thing in the morning, thanks!

Well, for anyone interested, the z-priority didn’t solve it for me. I had to create black rectangles that I placed behind the menu, and that did the trick.