I've found a way to reliably reproduce it: - Open Geany (no tabs saved, an empty document is opened) - Switch to non-latin layout - Enter random text - Shift+left+left to select some letters - Ctrl+C - Press left or right arrow to deselect - Mouse clicks: Edit - Preferences - Keybindings - Cancel - Shift+left+left+left to select another letters - Ctrl+C - Ctrl+V
"another letters" are replaced by "some letters", second Ctrl+C is ignored