In split window "End" and "Home" buttons does not work. Also some shortcuts, like "Ctrl-S". Please check if there are other keys and combinations which does not work properly. This is present in Geany from at very least 1.27.
Linux Mint 18.0 with latest patches, Geany 1.30.1 built from source.
$ ./geany -V geany 1.30.1 (built on 2017-06-03 with GTK 2.24.30, GLib 2.48.2)
$ ./geany -v & $ Geany-INFO: Geany 1.30.1, en_US.UTF-8 Geany-INFO: GTK 2.24.30, GLib 2.48.2 Geany-INFO: System data dir: /usr/local/share/geany Geany-INFO: User config dir: /home/pero/.config/geany Geany-INFO: System plugin path: /usr/local/lib/geany Geany-INFO: Added filetype Scala (61). Geany-INFO: Added filetype Genie (62). Geany-INFO: Added filetype CUDA (63). Geany-INFO: Added filetype Clojure (64). Geany-INFO: Added filetype Graphviz (65). Geany-INFO: Added filetype Cython (66). Geany-INFO: Added filetype JSON (67). Geany-INFO: Added filetype Arduino (68). Geany-INFO: Loaded libvte from libvte.so.9 Geany-INFO: Loaded: /usr/local/lib/geany/splitwindow.so (Split Window) Geany-INFO: Loaded: /usr/local/lib/geany/filebrowser.so (File Browser) Geany-INFO: unknown : None (UTF-8) Geany-INFO: Loaded /usr/local/share/geany/tags/std.py.tags (Python), 5964 symbol(s). Geany-INFO: Plugin "/usr/local/lib/geany/filebrowser.so" already loaded. Geany-INFO: Plugin "/usr/local/lib/geany/splitwindow.so" already loaded. Geany-INFO: Added 6 plugin(s) in '/usr/local/lib/geany'.