In Geany for Windows: There is a wrong behaviour of accented letters (e.g. Czech keyboard) when Caps lock is on: All accented letters like ě, š, č, ř, ž, ý, etc. are lower case while they should be upper case. It is known bug in Gtk+ https://bugzilla.gnome.org/show_bug.cgi?id=165385 but it was recently fixed and the fix was already released in Gtk+ 3.22.7 - see http://ftp.gnome.org/pub/gnome/sources/gtk+/3.22/gtk+-3.22.7.news
Please update the Gtk+ version used by Geany Windows builds to Gtk+ 3.22.7 to fix this bug in Geany for Windows.