I am running 10 Zorros parallel on a trading pc.
Very often I have the effect that some Zorro Gui windows are blind (White, broken), but Zorro is running correctly. Is there a dedicated command to repaint the window (also between the TF action for a new bar)?

What is happening in your scripts? I suspect you might have some heavy CPU processing going on.

If you invoke wait(0), you can force the GUI to refresh. Try it.
https://zorro-project.com/manual/en/sleep.htm