There is also another sizing bug. When you open some multitab window for the first time in a current workspace and try to change global scale, it resizes correctly first. But when you switch to another tab and try to change scale again, its width, let's say, "switches to another level". Looks like each tab has its own internal initial value of window width, and scaling triggers the window to set this internal value. If you resize the window manually before changing global scale, the bug disappears.
Also added to the list of issues (#34): 📣 WinBox 4 is here 📣 - #2428 by teslasystems