I have just noticed a variation in behaviour that I thought I would raise in case it triggers any ideas on this forum for fixing this.
As a reminder, the problem is that my app flickers when in a second user on the Mac whilst repositioning or scrolling container controls.
Opening multiple windows(B) of the same type within the same app, continues to show flicker across all windows. But when I open a different type of window(C), still within the same app, the flicker stops. And does not reappear when I close the window(C). Note that closing the window also removes it from the app by setting the referring property to nil.
Window(C) is a developer window, it tracks method calls within the app, and so is being continually updated by adding more lines to listboxes and therefore slows down the app a tad. Somehow its presence, or even the fact that it was there once, stops the flicker elsewhere.
Closing and restarting the app brings back flicker again.