I have reproduced this, but only when a control on the floating pane is active. When a control on the main Form is active, ProcessCmdKey gets called correctly. I believe this is correct as it looks like ProcessCmdKey only gets called on the parent chain of the active control.

Here is how you can make this work in your application: Move the logic from your Form's ProcessCmdKey override to a helper method, called something like ProcessCmdKeyHelper. Then define a custom control class which overrides ProcessCmdKey. In that override, also call off to ProcessCmdKeyHelper on the Form. Instead of docking your docked controls, dock instances of this custom control. Then place your docked controls in these custom controls and set their Dock properties to Fill.