Like in the title, https://bugs.kde.org/show_bug.cgi?id=482827 came back, this time this is happening to me on Wayland. Top floating panel, when one maximizes a window of an application, „un-floats”, but the part of the screen, where bottom of this floating panel was occupying and now taken by the maximized window, still receives mouse events (hover, click), in effect invisibly blocking interaction with top part of a maximized window, which, for example, makes difficult to click on its close button.