Just for clarification: Game Mode is the name of a Linux tool that can be enabled in RetroArch under Settings > Latency > Game Mode = ON
. But from your description you surely talk about the keyboard focus for RetroArch cores named Game Focus found under Settings > Input > Hotkeys > Game Focus (Toggle) = Key scroll_lock
?
I tested with Game Controller Hotkey DOWN + Select
on the C64 core, while Game Focus is enabled. I have it enabled for various computer systems too. The core successfully closes when using the shortcut on my system. Does your shortcut work when you disable Game Focus on the core?
Maybe you could look into the log, to see what happens the moment you press the shortcut? The easiest way would be to open a terminal, and run RetroArch from there and watch for any messages when you press the shortcut.