Action menu pops up if first disabled, then later enabled during a mouse click handler bound to "action"

[JB47394 30]

I'm disabling the normal action menu while I'm performing a user interaction (via uiInGameSetEventHandler).  I'm using the same keys and buttons as the action menu for this interaction ("action", "closeContext", "prevAction", "nextAction").  Every step of the interaction is flawless now except for one niggling little problem: if the user clicks the middle mouse button to complete the interaction, the interaction completes, but the action menu pops up.  This is not true of keyboard keys; if the interaction is completed by pressing space, then the action menu does not appear.

To be clear, both space and middle mouse button are defined as "action" keys.

I'm intercepting KeyDown and MouseButtonDown events, then using inputAction to spot the various actions that I want to override.  I've verified that I'm overriding the mouse click and the space.

Has anyone else seen this sort of asymmetry between mouse and keyboard events?  I'm not happy to have the quality of the user interaction damaged by this, but I can live with it.