I've merged this with the older topic it's a part of/related to.
This isn't the first time it's happened, but unfortunately no amount of save data or logs can shed light on this since it's purely a bug in the UI state--the game logic and animations and everything will run fine. It depends on some exact key presses to cause the UI to enter a state where it no longer accepts input, but it's so rare that we have no known way of repeating it.
Somehow on the main UI it's still possible to enter this state, but the UI has so many possible states that I don't know which combination could cause this :/.
Ideally this would happen to me sometime, so that I can just attach the debugger and closely examine the state, but so far I've never seen it xD (having the game produce enough of the right diagnostic data to reliably debug it remotely would be tough). As for others who encounter it, they'd have to remember their exact sequence of key presses before it happened, and be able to repeat it, before I could possibly do so here.