Cubase UI thread killing processor on MacOS 12

When it is about serious mixing when there are alot of VST instruments and plugins, when audio performance is close to 90%, then Cubase main window makes CPU to be overloaded, and sound interruptions occurs.

If I minimise Cubase main window, then sound plays without any interruptions. If I open it again, then interruptions occurs again. I think it is related to main UI thread: it redraws main window content. But when it is collapsed then no CPU is used to redraw UI.

iMac , OSX 12.0.1, 64 GB, 4,2 GHz Quad-Core Intel Core i7, Radeon Pro 580 8 GB

Indeed it redraws the main window content, that what it is made for…
If your system is maxed out, everything what changes the high load a bit could make a difference.