menu item "copy" leads to a reduced Notepad++ window.
It’s a long time I hope this little & spectacular bug to be fixed. Under Windows (all version of Windows) when you select the “Copy” item menu while some thing like a word is selected, your notepad++ window disappears. Then if you look to the top-left corner of your screen desktop you will see a little Windows window in a minimal size which is the minimal size allowed by Windows. If you drag this window to enlarge it, you will see your notepad++ window. This doesn’t occur if you choose the “Cut” item.
It’s a long time I hope this little & spectacular bug to be fixed.
It’s probably hard to fix a bug that likely happens to exactly one person (you) and that person hasn’t reported it to the official issues list. Or maybe you have?