Using Reader DC 2021.001.20145 on Windows 10 (20H2) in Desktop mode (tablet mode off).

When accessing system menu (restore, move, size, minimize, maximize, close) by clicking icon in upper left of window, the menu items work fine. But when accessing the same menu from the taskbar (hover, wait for popup, right-click on pop-up), the functions are ignored (minimize, move, size), act differently (close), or act strangely (maximize).