DosBox 0.74.2 from rapps does not draw any content to the window anymore after switching back from fullscreen

DosBox 0.74.2 from rapps.
0.4.11-RC-30-g83e4a61 affected
and everything down to at least
SVN r72748 is affected as well.
I know the issue since long time, unfortunately mentioned it just as a remaining thing in historic CORE-11245. Imho it deserves its own ticket.

VBox4.3.12 + VBEMP + inbuilt Mesa

Reproduction steps
-set desktop resolution to 800x600 32bpp
-start DosBox main app (it will start windowed by default)
-Hit Alt+Enter, it will properly switch to fullscreen (side-note: leaving the taskbar visible)
-Release the Alt-Key (yes that's also necessary on Windows)
-Hit Alt+Enter again

Expected result
It returns into windowed mode, and continues to draw content
Like Windows XP SP3 does. xpsp3_ok.webm

Observed result
It returns into windowed mode, but stops drawing anything into the window.
0.4.11-RC-30-g83e4a61__dosbox.webm
0.4.11-RC-30-g83e4a61__dosbox.log

(Even minimizing/maximizing or moving the window offscreen will not fix it).