I've just tested that myself on corporate Win7 PC and it works in the case where a scroll made the 3d plot disappear, and then a click inside makes it re-appear.
Further, I did NOT need to restart mathcad. I could just right click the desktop, select the "personalise", then scroll down to the Basic & High Contrast Themes, and select one (usually classic), and on applying the theme, Mathcad worked right. I could change the theme again (back to one of the fancy ones) and Mathcad (still running) would stop doing the proper re-draw!
So yes it works.
Just got to check a colleagues machine (slightly older / different graphics card) to see if it works for him.
see also this other thread that I started blank 3d plot - PTC Community Its a nice link back 😉
