This problem cannot be reproduced under normal working conditions. The maximization limit does not change when you maximize or iconize an image window, or after a process is executed. We also use 4K, 5K and 8K monitors regularly, and this problem never happens, on any platform.
The maximization limit changes to its default position when the application's main window is resized. This is not a bug, but a protection feature to prevent too small maximization regions on the workspace, which may cause problems if the main window is resized to very small dimensions. If you use PixInsight's main window unmaximized, that is, not occupying your entire desktop, its dimensions may change spontaneously under some situations. If you have too many tool bars and status bars open, sometimes the main window may need to grow to fit status information for the current image. We'd need to see a screenshot of your main window setup to say more.
We can think on ways to improve this behavior for future versions. Anyway, you can move the maximization limit with the mouse very easily in a second. I wouldn't regard this as 'irritating', although this is of course subjective.
