Thanks for the report, this one was real. The construction window can be dragged past the edge of the game window, and when it is, it turns into its own window on your desktop. Clicking a recipe in it then left the keyboard with that window, so TAB and every other game key went nowhere until a click on the world handed the keyboard back, which is exactly the build attempt you noticed.
Game keys pressed while that popped-out window has the keyboard now reach the game, so TAB rotates the cade straight after you pick it, and the other hotkeys work from there too. The window still lives wherever you drag it.
Revision: master commit db7eb1ace, in-game version v0.1.5993 and later (the grey version string top-right in the client). It will be in the next build pushed to the launcher.